LIBRARY 


UNIVERSITY  OF  CALIFORNIA. 


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iii 


THE  AIR  AND  VENTILATION 
OF  SUBWAYS 


BY 

GEORGE  A.  SOPER,  PH.D. 

MEMBER    AMERICAN    SOCIETY    OF    CIVIL    ENGINEERS, 

AMERICAN     CHEMICAL     SOCIETY,     SOCIETY    OF 

AMERICAN   BACTERIOLOGISTS,   AMERICAN 

PUBLIC    HEALTH    ASSOCIATION 


FIRST  EDITION 

FIRST    THOUSAND 


NEW   YORK 

JOHN   WILEY    &   SONS 

LONDON:    CHAPMAN    &    HALL,    LIMITED 

1908 


c::.  • 


COPYBIQHT,    1908, 

BY 
GEORGE   A.  SOPER 


Stanhope  ipreaa 

F.    H.  G1LSON     COMPANY 
BOSTON.     U.S.A. 


PREFACE 


THIS  volume  is  the  outcome  of  studies  carried  on  for  two 
and  one-half  years  for  the  Board  of  Rapid  Transit  Railroad 
Commissioners  for  the  City  of  New  York  and,  after  that 
board  went  out  of  existence,  for  the  Interborough  Rapid 
Transit  Company  to  whom  the  first  New  York  subway  is 
leased.  The  work  was  begun  in  the  summer  of  1905  and 
concluded  in  1907. 

The  original  data  covering  about  2000  pages  have  never 
been  published,  although  reports  summarizing  many  of 
the  facts  have  appeared  in  the  official  transactions  of  the 
Rapid  Transit  Commissioners  or  been  read  by  the  author 
before  the  Society  of  Arts  of  Boston,  the  New  York 
Academy  of  Medicine  or  elsewhere. 

At  the  conclusion  of  the  investigations  it  seemed  desir- 
able to  have  some  of  these  reports  bound  together  for 
private  circulation,  but  it  was  finally  decided  to  put  the 
work  into  somewhat  more  extended  form  and  offer  it  to  the 
general  public. 

It  has  seemed  desirable  to  preface  the  description  of  the 
investigation  by  a  few  facts  concerning  the  scientific 
ground-work  upon  which  the  solution  of  problems  of 
ventilation  should  be  based,  and  to  this  end  the  composi- 
tion of  good  and  bad  air,  some  mechanical  principles  of  the 
atmosphere  and  other  matters  have  been  included.  The 
object  throughout  has  been  to  make  available  in  con- 
venient form  an  account  of  the  essential  features  of  the 

iii 

178215 


iv  PREFACE 

investigation  in  the  hope  that  the  information  may  be  of 
service  to  persons  not  necessarily  trained  in  sanitary 
science  but  interested  in  knowing  what  good  and  bad  air 
consists  in  and  how  to  deal  with  it  in  subways  and  other 
enclosed  spaces. 

G.  A.  S. 


CONTENTS 


CHAPTER  I 
SUBWAYS  AND  THE  PUBLIC  HEALTH 

Evolution  of  the  Modern  Subway:  PAGE 

NEW  LONDON  TUBES 3 

PARIS  SUBWAYS 4 

BERLIN  SUBWAYS 4 

OTHER  EUROPEAN  SUBWAYS 5 

AMERICAN  SUBWAYS      5 

UNDERGROUND  ADJUNCTS  OF  SUBWAYS 7 

EFFECTS  OF  SUBWAYS  ON  CONGESTION  OF  POPULATION    ...  9 

The  Bearing  of  Subways  on  Health 11 


CHAPTER  II 
CHARACTERISTICS  OF  GOOD  AIR   AND  BAD  AIR 

The  Atmosphere  of  the  Open  Country: 

THE  RESERVE  SUPPLY  OF  PURE  AIR 13 

GASES  OF  THE  NORMAL  ATMOSPHERE 14 

ODORS 15 

CARBON  DIOXIDE 17 

WATER  VAPOR 18 

OPTIMUM  CONDITIONS  OF  MOISTURE,  COLD  AND  HEAT   ....  19 

DUST 20 

FORMS  OF  LIFE 22 

The  Air  of  Towns  and  Cities: 

AIR  OF  LONDON,  PARIS  AND  NEW  YORK 24 

UNWHOLESOME  GASES 26 

COMPOSITION  OF  CITY  DUSTS 28 

EFFECTS  OF  ATMOSPHERIC  IMPURITIES  IN  CITIES 29 

FREQUENCY  OF  DISEASE  DUE  TO  INFECTED  AIR 32 

v 


Vi  CONTENTS 

The  Air  of  Confined  Spaces:  PAGE 

COMPOSITION  OF  RESPIRED  AIR 32 

CAUSE  OP  UNPLEASANT  ODORS      34 

AMOUNT  OF  CARBON  DIOXIDE  PRODUCED  BY  HUMAN  BEINGS    .  35 

VALUE  OF  ANALYSES 36 

HEAT  PRODUCED  BY  HUMAN  BEINGS 37 

MOISTURE  PRODUCED  BY  HUMAN  BEINGS 38 

AMOUNT  OF  SPACE  REQUIRED  FOR  DECENCY,  COMFORT  AND 

SAFETY .    .  39 

SUPPLY  OF  AIR  REQUIRED      41 

THE  DEMAND  FOR  BETTER  CONDITIONS 41 

STANDARDS  OF  PURITY  FOR  THE  AIR  OF  SUBWAYS 42 

CALCULATION  OF  FRESH  AIR  REQUIREMENTS 44 

EFFECTS  OF  BAD  VENTILATION      45 


CHAPTER  III 
METHODS  OF  VENTILATING  SUBWAYS 

Fundamental  Considerations : 

DIFFERENCES  IN  THE    PROBLEMS  OF  VENTILATING  SUBWAYS, 

TUNNELS  AND  MINES .       48 

NECESSITY  FOR  SKILL  IN  DESIGN  AND  MAINTENANCE    ....       49 

PHYSICAL  PRINCIPLES  INVOLVED 49 

MECHANICAL  PRINCIPLES 50 

PHYSICAL    PRINCIPLES    INVOLVED  IN  SUBWAY  HEATING  AND 
COOLING 53 

Practical  Systems  in  Use : 

THE  EXHAUST  AND  PLENUM  PRINCIPLES 54 

ACTION  OF  FANS  APPLIED  AT  VARIOUS  POINTS 55 

ACTION  OF  FANS  APPLIED  AT  ONE  END  OF  A  SUBWAY    ....  61 

NATURAL  VENTILATION      62 

THE  PISTON  ACTION  OF  TRAINS  64 


CHAPTER  IV 
THE  AIR  OF  EUROPEAN  SUBWAYS 

Metropolitan  and  District  of  London : 

WORK  OF  AN  OFFICIAL  INVESTIGATING  COMMITTEE 72 

OPERATING  CONDITIONS 73 

COMPANY'S  EXPERIMENTS  WITH  VENTILATION 74 

NATURAL  VENTILATION  75 


CONTENTS  Vll 

Metropolitan  and  District  of  London  :  —  continued  PAGE 

CONDITION  OF  THE  AIR  ..........    .    ......  75 

HEALTH  OF  EMPLOYEES      .......                   .....  77 

METHODS  OF  VENTILATION  STUDIED  BY  THE  COMMITTEE  ...  77 

FINAL  CONCLUSIONS  OF  THE  COMMITTEE     ........  79 

The  Parallel  Tubes  of  the  Central  London  Railway  : 

CONSTRUCTION     ...........  80 

METHOD  OF  VENTILATION      ...............  80 

CHEMICAL  CONDITIONS   .......... 

BACTERIOLOGICAL  CONDITIONS     .............  82 

CONCLUSIONS  .....................  83 

City  and  South  London  Railway      ..............  83 

The  Metropolitan  Railway  of  Paris     .............  84 


Results  of  an  Inspection  of  European  Subways  in 

SENSIBLE  CONDITION  OF  THE  AIR     ............  00 

ROADBEDS    ......................  92 

ODOR    ........................  93 

TEMPERATURE     ....................  93 

DUST    ........................  96 

MOLDS  ........................  97 

VENTILATION  .....................  97 

HEALTH  OF  EMPLOYEES  .......  98 


CHAPTER  V 

THE  AIR  OF  THE  NEW  YORK  SUBWAY 

Scope  of  the  Investigation 100 

Essentials  of  Construction  and  Operation  at  the  Time  of  the  Inves- 
tigation : 

STEEL  AND  CONCRETE  IN  THE  SUBWAY 103 

PART  OF  SUBWAY  IN  OPERATION 104 

SECTION  CHOSEN  FOR  CLOSEST  OBSERVATION 104 

NATURE  OF  THE  TRAVEL 106 

SANITARY  FEATURES  OF  CONSTRUCTION 109 

PROVISIONS  FOR  VENTILATION 113 

PHENOMENA  OF  VENTILATION 115 

Temperature  and  Humidity: 

METHODS  EMPLOYED 123 

RESULTS  OF  TEMPERATURE  AND  HUMIDITY  OBSERVATIONS  .    .  129 

HUMIDITY    ,  135 


viii  CONTENTS 

CHAPTER  VI 
THE  AIR  OF  THE  NEW  YORK  SUBWAY  (Continued) 

Chemical  Condition  of  the  Air :  PAGE 

METHODS  OF  ANALYSES      139 

CARBON  DIOXIDE  RESULTS 147 

OXYGEN  RESULTS 154 

Bacterial  Condition  of  the  Air : 

QUANTITATIVE  METHODS  OF  ANALYSIS 155 

ADDITIONAL  BACTERIAL  WORK 161 

RESULTS 164 

Odors : 

METHODS  OF  INVESTIGATION 172 

RESULTS  OF  INVESTIGATING  THE  CAUSES 172 

Dust: 

METHODS  OF  EXAMINATION 178 

ULTIMATE  NUMBER  OF  DUST  PARTICLES 181 

RESULTS 183 

Conclusions 189 

CHAPTER  VII 

HEALTH    OF   NEW  YORK  SUBWAY    EMPLOYEES 

Plan  of  the  Investigation 195 

The  Condition  of  the  Air: 

PHYSICAL  AND  CHEMICAL  COMPOSITION  OF  THE  DUST   ....  197 

BACTERIAL  COMPOSITION  OF  THE  AIR  AND  DUST 198 

SOURCES  OF  THE  IRON  DUST 198 

WEIGHT  OF  DUST  IN  AIR 199 

WEIGHT  OF  DUST  INHALED 200 

THE  DANGERS  OF  THE  DUST 201 

INJURIOUS  PROPERTIES  OF  SUBWAY  DUST 201 

CONTRIBUTING  FACTORS 202 

NATURAL  DEFENSES  AGAINST  DUST •  203 

CONDITION  OF  THROATS  AND  LUNGS  OF  CITY  DWELLERS   .    .    .  204 

DISEASE  DUE  TO  IRON  DUST 205 

Description  of  the  Subway  Employees: 

PHYSICAL  APPEARANCE  OF  THE  MEN 207 

REGULAR  DUTIES  OF  THE  MEN 208 

MEDICAL  HISTORY  BEFORE  AND  AFTER  ENTERING  SUBWAY 

EMPLOYMENT  .                             209 


CONTENTS  IX 

PAGE 
Results  of  the  Physical  Examinations  of  the  Employees: 

EXAMINATION  OF  PRINCIPAL  ORGANS  AND  EYES 210 

EXAMINATION  OF  THE  UPPER  AIR  PASSAGES 210 

EXAMINATION  OF  THE  LUNGS 211 

Results  of  Analyses  of  Sputum,  Urine  and  Sweat: 212 

Results  of  the  Autopsies 213 

Possible  Causes  and  Consequences  of  the  Pleurisy  Found: 

PLEURISY  AMONG  THE  SUBWAY  EMPLOYEES 218 

NORMAL  AMOUNT  OF  PLEURISY  AMONG  CITY  DWELLERS    .    .    .  220 

CAUSE  OF  THE  PLEURISY 225 

Conclusions 225 

Recommendations 228 


THE  AIR  AND  VENTILATION  OF 
SUBWAYS 

CHAPTER  I 

SUBWAYS  AND  THE  PUBLIC   HEALTH 

THE  development  of  subways  as  a  means  of  facilitating 
the  movement  of  people  from  point  to  point  within  the 
limits  of  a  single  city  forms  an  interesting  chapter  in  the 
history  of  modern  transportation.  Placed  in  the  last  few 
years  upon  a  successful  basis  as  a  result  of  operating  and 
structural  devices  not  before  practicable,  nearly  all  the 
largest  cities  now  possess  one  or  more  subways  and  scores 
of  smaller  places  are  planning  them. 

In  the  construction  of  subway  systems,  London,  the 
most  populous  city,  has  at  all  times  held  first  rank.  Not 
only  were  the  first  subways  built  there,  but,  in  face  of 
repeated  failure,  subway  construction  was  persisted  in  in 
London  until  it  became  a  popular  success.  To-day  there 
are  more  types  of  subways  in  London,  and  a  greater  aggre- 
gate mileage  of  them,  than  can  be  found  in  any  other  city. 

EVOLUTION  OF  THE  MODERN  SUBWAY 
The  first  important  tunnel  built  solely  for  the  trans- 
portation of  passengers  from  one  part  of  a  city  to  another 
ran  under  the  Thames  in  London  about  two  miles  below 
London  Bridge.  The  object,  as  in  several  other  river 
tunnels  which  were  built  in  early  times,  was  merely  to 
afford  means  of  passing  from  one  shore  to  another  and  not 
to  connect  with  any  surface  transportation  system. 

l 


2  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

This  first  subway  was  begun  in  1824  and  was  opened  in 
1843.  The  cost  was  about  $2,340,000.  It  was  intended 
for  horse-propelled  vehicles  as  well  as  foot  passengers.  It 
was  1200  feet  long,  14  feet  wide  and  16  feet  4  inches  high. 
There  were,  in  fact,  two  parallel  tunnels  of  these  dimensions, 
running  side  by  side,  separated  by  a  masonry  pier  4  feet 
thick.  The  undertaking  paid  so  poorly  that  the  receipts  were 
scarcely  sufficient  to  meet  the  cost  of  repairs.  This  road 
now  forms  part  of  the  East  London  Railway  having  been 
purchased  in  1865  for  less  than  one-half  the  original  cost. 

The  first  subway  to  be  provided  with  its  own  vehicles 
for  transporting  passengers  was  constructed  in  1863  under 
the  Thames  near  the  Tower  Bridge.  This  tunnel  was  a 
circular  iron  tube  composed  of  segments  bolted  together 
and  was  7  feet  in  diameter  and  1350  feet  long.  As  in 
modern  tube  railways,  passengers  were  taken  up  and  down 
in  elevators  through  shafts.  These  were  10  feet  in  diameter 
and  60  feet  deep.  Transit  from  one  end  of  the  tunnel  to 
the  other  was  accomplished  on  a  single  track  by  means  of 
cars  hauled  by  wire  ropes.  This  subway  was  closed  to 
passengers  in  1897  and  is  now  used  for  a  gas  main. 

In  view  of  the  failure  of  these  two  tunnels  to  meet 
popular  favor,  it  is  interesting  to  note  the  complete  success 
of  the  Blackwall  tunnel  which  runs  under  the  Thames 
about  six  miles  below  London  Bridge.  It  was  opened  in 
1897  and  is  used  by  passengers  and  pedestrians.  The 
total  length  is  6210  feet,  of  which  1740  feet  are  approaches. 
This  tunnel  is  next  to  the  largest  shield-driven  tube  in 
existence,  being  27  feet  outside  diameter.  The  inside  is 
lined  with  light-colored  glazed  tiles  and  is  paved  with 
granite  blocks  on  the  inclines  and  with  asphalt  elsewhere. 
It  is  well  lighted  and  the  air  is  agreeable,  ventilation  taking 
place  through  large  shafts  on  the  two  opposite  shores. 


SUBWAYS  AND  THE  PUBLIC  HEALTH       3 

The  first  extensive  underground  railway  which  can 
properly  be  termed  a  system  was  the  Metropolitan  and 
District  of  London.  Its  object  was  to  carry  the  public 
more  expeditiously  and  comfortably  from  place  to  place 
within  the  city  than  could  be  accomplished  on  the  surface. 
This  road  was  opened  from  Paddington,  the  terminus  of 
the  Great  Western  Railway,  to  Farringdon  Street  in  the 
business  district,  in  1863.  Extensions  were  numerous  up  to 
1884,  at  which  time  the  system  had  been  so  developed  as  to 
form  a  complete  circle  around  the  inner  portions  of  the  city. 

To-day,  the  Metropolitan  is  almost  the  only  example 
in  London  of  a  shallow  railroad  subway,  that  is,  one  built 
near  the  surface  of  the  ground  and  reached  by  stairways. 
All  the  rest,  and  there  are  six  more,  have  been  built  in  the 
London  clay  at  depths  which  vary  from  40  to  150  feet  below 
the  surface. 

The  pioneer  deep  tube  subway  under  city  streets  was  the 
City  and  South  London  and  was  opened  for  traffic  in  1890. 
It  is  about  three  miles  long  and,  like  practically  all  deep- 
lying  roads,  is  composed  of  two  metal-lined  tubes  running 
side  by  side.  This  road  has  been  very  successful,  carrying 
in  the  first  year  of  operation  about  2,400,000  passengers. 
It  was  the  first  important  city  subway  to  be  operated  by 
electricity.  The  original  intention  was  to  use  an  endless 
cable  for  moving  the  trains. 

New  London  tubes.  By  far  the  best  known  and  one  of 
the  most  profitable  deep  subways  is  the  Central  London 
which  was  opened  in  1900.  After  this  came  the  Great 
Northern  and  City,  opened  in  1904,  the  Waterloo  and  City, 
the  Baker  Street  and  Waterloo,  the  Great  Northern, 
Piccadilly  and  Brompton  and  the  Charing  Cross,  Euston 
and  Hampstead. 


4  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

The  average  internal  diameter  of  these  deep  tubes  is  11 
feet  6  inches.  They  occasionally  follow  steep  grades  and 
curve  about  continually.  The  different  roads  are  fre- 
quently connected  at  stations  by  passageways  for  foot 
passengers. 

Paris  subways.  Following  the  example  of  London,  the 
city  of  Paris,  in  1898,  laid  out  an  elaborate  plan  for  subways. 
The  road  was  built  to  relieve  the  lack  of  public  transpor- 
tation facilities  in  Paris  itself  and  to  develop  poorly 
populated  and  distant  quarters  in  the  suburbs.  It  was  at 
first  thought  that  only  a  part  of  the  whole  plan  would 
be  carried  out,  but  the  success  which  followed  the  open- 
ing of  the  road  was  so  great  that  it  was  at  once  decided 
to  finish  the  entire  system.  Passengers  were  first  carried 
in  1901. 

Unlike  most  of  the  London  roads,  the  Paris  subways 
belong  to  the  type  which  runs  close  beneath  the  surface  of 
the  ground,  are  built  of  masonry,  have  two  or  more  tracks 
and  are  reached  by  stairways  from  the  streets.  Since  the 
opening  of  the  Paris  system,  extensive  construction  has 
been  in  progress  both  by  the  city  and  by  private  capital, 
so  that,  at  the  present  time,  Paris  has  the  second  greatest 
aggregate  underground  railroad  mileage  of  any  city. 

Berlin  subways.  The  city  of  Berlin  is  provided  with  a 
combined  subway  and  elevated  system  which  was  opened 
for  traffic  in  1902.  It  is  one  of  three  roads  which  run  partly 
overhead  and  extends  through  the  central  part  of  the  city 
from  east  to  west.  The  tunnels  were  constructed  under 
the  streets,  the  top  sometimes  approaching  to  within  2 
feet  of  the  surface.  The  subway  system  was  considerably 
extended  in  1907. 


SUBWAYS  AND  THE  PUBLIC  HEALTH  5 

Other  European  subways.  The  city  of  Budapest  has  an 
electric  underground  railway  about  two  miles  in  length 
opened  in  1896.  It  is  a  double-tracked,  overhead  trolley 
system  built  near  the  surface  of  the  ground  and  in  design 
resembles  the  subways  of  Boston,  New  York  and  Phila- 
delphia. 

Glasgow  has  a  subway  six  miles  long  partly  of  the  deep, 
and  partly  of  the  shallow,  type. 

Many  other  important  subways  now  exist  in  Europe. 
Some  belong  to  the  period  of  earliest  construction,  while 
others  are  of  a  newer  type.  Nearly  all  are  operated  by 
electricity. 

American  subways.  Aside  from  the  terminal  connec- 
tions of  trunk  line  railroads,  the  first  underground  city 
railroad  in  America  was  built  in  Boston  and  was  begun  in 
1895.  This  road  runs  under  the  business  part  of  the  city 
with  a  branch  under  the  harbor  and  accommodates  several 
lines  of  trolley  cars  as  well  as  trains  of  the  Boston  Elevated 
System.  It  is  not  provided  with  its  own  cars  but  is  used 
by  outside  lines  which  otherwise  would  run  on  the  surface 
and  interfere  with  street  traffic.  It  was  estimated  that  at 
least  50,000,000  passengers  used  the  original  subway  during 
the  first  twelve  months  after  its  completion  and  its  use  has 
apparently  increased  since  then  by  over  60  per  cent. 

The  New  York  subway  was  opened  in  1904.  It  was 
considered  to  be  the  most  perfect  example  of  subway  con- 
struction yet  afforded  and  was  expected  to  play  an  impor- 
tant part  in  relieving  the  congestion  which  is  rapidly 
growing  at  the  southern  end  of  Manhattan  Island.  It  is, 
like  most  subways,  chiefly  of  the  shallow  type.  A  descrip- 
tion of  its  principal  features  will  be  found  beyond.  (See 
Figs.  1  and  2.) 


6 


THE  AIR  AND   VENTILATION  OF  SUBWAYS 


SUBWAYS  AND  THE  PUBLIC  HEALTH        7 

An  account  of  the  plans  for  the  development  of  under- 
ground and  under-water  transportation  in  New  York  which 
have  followed  the  opening  of  the  first  subway  would  pass 
the  limits  of  space  of  this  volume.  They  include  roads 
under  the  Hudson  river  and  East  river  and  extensions  of 
the  original  line  aggregating  many  miles  in  length. 

The  history  of  the  construction  of  city  subways  shows 
that  although  underground  roads  were  built  over  fifty 
years  ago,  it  was  not  until  electric  traction  became  prac- 
ticable, bringing  with  it  the  possibility  of  good  air,  that 
city  subways  on  a  large  scale  were  successful.  It  is  interest- 
ing to  note  that  the  key  to  success  depended  largely  upon 
the  question  of  sanitation.  Subways  could  not  be  made 
even  tolerably  agreeable  so  long  as  it  was  necessary  to  light 
them  by  oil  and  propel  the  cars  by  means  of  coal-burning 
locomotives.  To  such  conditions  no  public  could  be 
expected  to  become  indifferent.  On  this  point  the  history 
of  the  Metropolitan  of  London  is  conclusive. 

Underground  adjuncts  of  subways.  In  the  rapid  growth 
of  subways  which  has  here  been  outlined,  the  construction 
has  not  been  confined  to  the  simple  form  of  structure 
originally  adopted.  Both  with  respect  to  main  lines  and 
auxiliary  passages,  developments  have  been  made  which 
are  of  considerable  interest  when  viewed  from  a  sanitary 
standpoint. 

The  New  York  subway  differs  from  most  foreign  roads 
in  having  four  tracks  instead  of  one  or  two,  in  being  provided 
with  express  as  well  as  local  services,  in  having  underground 
stations  with  elaborate  toilet  room  facilities  and  in  having* 
numerous  underground  connections  with  office  buildings 
and  shops.  These  lateral  connections  sometimes  run  for 
considerable  distances  through  the  basements  of  sky- 


THE  AIR  AND  VENTILATION   OF  SUBWAYS 


SUBWAYS  AND  THE  PUBLIC  HEALTH       9 

scraper  office  buildings,  hotels  and  shops.  The  passages 
often  accommodate  barber  shops,  restaurants,  news  stands, 
fruit  and  candy  stands,  soda  fountains  and  flower  booths. 

The  lateral  underground  passages  of  the  deep  London 
tubes  are  often  long  and  devious,  but  they  are  used  only 
by  pedestrians  and  do  not  contain  shops.  On  the  station 
platforms  of  practically  all  subways  are  automatic  vending 
and  weighing  machines.  The  articles  sold  are  innumerable 
in  variety. 

It  is  needless  to  remark  that  in  all  these  lateral  sub- 
terranean passages  the  sun  never  penetrates  and  it  is  always 
night.  Fresh  air  enters  only  through  doors  and  through 
elevator  shafts.  The  air  is  usually  cool.  The  volumes  of 
air  passing  are  often  very  large.  Where  candy,  fruit  and 
other  food  is  sold  it  is  usually  quite  unprotected  from  the 
dust  and  air. 

Effects  of  subways  on  congestion  of  population.  It  would 
be  interesting,  if  space  permitted,  to  discuss  the  effect  on 
congestion  of  population  which  the  construction  of  under- 
ground railroads  for  urban  intercommunication  has  pro- 
duced. It  would  be  seen  that  the  ultimate  effect  has  been 
quite  opposite  to  that  sometimes  intended,  for,  instead  of 
relieving  congestion,  they  have  increased  it.  If  the  sub- 
ways have  given  new  outlets  from  the  overcrowded  sections 
of  cities  to  the  more  sparsely  settled  ones,  they  have  also 
provided  means  by  which  the  overcrowded  places  can  be 
more  rapidly  reached  than  formerly,  with  the  result  that 
the  worst  places  have  been  still  further  congested.  This 
added  congestion  means  serious  inconvenience  and  possibly 
injury  to  the  public  health. 

Some  of  the  inconvenience  which  results  from  congestion 
is  but  too  evident  to  every  person  who  visits  the  business 


10  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

districts  of  a  great  city  during  business  hours.  The  streets 
are  so  crowded  that  pedestrians  overflow  from  the  side- 
walks upon  the  carriageways  and  there  is  so  little  room  on 
the  carriageways  that  vehicles  are  able  to  thread  their  way 
only  with  difficulty  and  at  greatly  reduced  speed. 

Nor  does  the  effect  of  this  crowding  bear  only  on  the 
mere  convenience  of  the  public.  It  interferes  seriously 
with  the  conduct  of  trade.  This  means  loss  of  money. 
Sir  John  Wolfe-Barry  *  and  Mr.  R.  G.  H.  Davison  have  cal- 
culated that  the  loss  of  time  experienced  through  the  con- 
gested condition  of  London  streets  affects  persons  whose 
annual  aggregate  earning  capacity  is  £173,291,000  and  of 
vehicles  whose  time  is  valued  at  £16,562,000  annually.  If 
the  loss  of  time  to  each  one  of  these  wage  earners  is  only 
five  minutes  in  each  day  of  eight  hours,  the  total  loss  in 
money  which  would  be  produced  in  a  year  would  be 
£1,898,534.  It  is  not  improbable  that  the  actual  loss  is 
much  greater. 

Careful  studies  in  America  and  Europe  as  to  the  causes 
and  remedies  for  overcrowded  streets  have  been  carried  on 
by  a  Royal  Commission  on  London  Traffic,  and  an  advisory 
board  composed  of  Sir  John  Wolfe-Barry,  Sir  Benjamin 
Baker  and  William  Barclay  Parsons,  engineers  of  inter- 
national reputation,  have  shown  in  a  report  to  this  com- 
mission that  by  bringing  more  and  more  people  from  the 
immediate  suburbs,  the  development  of  city  railways  has 
increased  congestion  to  such  a  point  that  it  is  now  necessary 
to  widen  streets,  plan  for  proper  sub-structures  beneath 
the  streets  and  regulate  the  heights  of  buildings  if  more 
serious  consequences  to  the  commercial  welfare  of  the  city 
are  to  be  avoided. 

1  Memorandum  by  Sir  John  Wolfe-Barry,  K.C.B.,  and  Mr.  R.  G.  H. 
Davison,  M.  Inst.  C.  E.  in  Appendix  to  Report  of  Advisory  Board  of 
Engineers  to  Royal  Commission  on  London  Traffic,  pp.  675-6,  Vol.  8. 


SUBWAYS  AND  THE  PUBLIC  HEALTH       11 

THE  BEARING  OF  SUBWAYS  ON  HEALTH 

A  study  of  all  the  effects  of  subway  conditions  on  public 
health  would  form  an  extremely  difficult  inquiry  and 
obviously  can  only  be  dealt  with  here  in  a  most  general 
manner. 

Vital  statistics  are  not  available  to  show  the  state  of 
health  of  persons  who  use  subways  as  compared  with  those 
who  do  not,  nor  are  facts  at  hand  to  indicate  differences  in 
public  health  which  can,  with  certainty,  be  ascribed  to 
underground  railways. 

For  practical  purposes,  it  is  probably  safe  to  assume 
as  a  groundwork  of  inquiry  that  if  subways  produce  evil 
effects  upon  the  health  of  the  traveling  public,  these 
effects  are  due  to  overcrowding  or  some  harmful  quality  of 
the  subway  air. 


CHAPTER  II 

CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR 
THE  ATMOSPHERE  OF  THE  OPEN  COUNTRY 

So  far  as  known,  there  is  only  one  constituent  of  the 
atmosphere  which  is  directly  useful  to  living  beings  and 
this  is  oxygen.  The  other  gases  are  not  immediately 
necessary,  although  they  perform  many  indispensable 
functions  in  the  economy  of  nature. 

The  essential  act  of  respiration  is  an  absorption  of  oxygen 
and  a  production  of  carbon  dioxide.  It  is  natural  to  think 
of  this  exchange  as  one  which  takes  place  only  in  the  lungs, 
but  it  is  really  common  to  all  the  myriad  cells  of  the  body. 
The  lungs  act  simply  as  central  exchange  depots;  the 
distant  cells  are  the  real  laboratories. 

The  principal  gases  of  the  atmosphere  are  present  in  a 
mechanical  mixture  and  not  in  chemical  combination  with 
one  another.  A  portion  of  the  oxygen  may  be  abstracted 
without  affecting  the  other  constituents  and  other  gases 
may  be  added  without  affecting  the  oxygen.  'Oxygen 
has  always  the  same  properties  whether  it  is  freshly 
prepared  or  not.  Fresh  air  is  simply  air  which  is  uncon- 
taminated. 

Were  it  not  that  the  atmosphere  is  being  constantly 
and  vigorously  agitated,  and  an  incessant  mixture  taking 
place  through  the  operation  of  the  physical  principles 
known  as  diffusion  and  convection  and  the  action  of  winds 
and  lesser  air  currents,  human  existence  in  cities  and 

12 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      13 

houses  would  be  impossible  and  life  on  any  part  of  the 
earth's  surface  would  cease  to  exist. 

The  reserve  supply  of  pure  air.  Inasmuch  as  heavy 
draughts  are  made  upon  the  supply  of  oxygen  by  living 
creatures  and  by  the  combustion  of  fuel,  to  say  nothing  of 
the  impurities  produced,  it  is  evident  that  the  supply  in 
inhabited  places  must  be  continuously  renewed.  The  open 
country,  the  sea  and  the  upper  atmosphere  are  the  great 
reservoirs  of  pure  air. 

How  great  is  this  reserve  is  not  certain,  for  the  height  of 
the  atmosphere  above  the  earth  is  not  known  with  exact- 
ness. It  was  formerly  supposed  that  it  extended  to  a 
depth  of  about  fifty  miles,  but  observations  of  meteors, 
which  are  believed  to  grow  luminous  through  heat  generated 
by  friction  with  the  air  of  the  earth,  have  led  to  the  belief 
that  the  atmosphere  extends  even  to  a  greater  height  than 
one  hundred  miles. 

It  has  often  been  suggested  that  the  oxygen  of  the 
atmosphere  might,  in  time,  become  exhausted,  and  many 
ingenious  calculations  have  been  made  with  respect  to  this 
subject.  For  example,  it  has  been  calculated  by  Remsen 
that,  assuming  the  population  of  the  earth  to  be  1000 
million  human  beings,  the  quantity  of  oxygen  used  in 
respiration  in  a  year  amounts  to  about  s.FffV'tfUT  part  of  the 
supply.  Supposing  that  the  quantity  of  oxygen  required 
for  other  purposes  is  nine  times  this,  then  the  total  amount 
used  up  in  a  year  would  be  only  3-3^  jnnr  of  the  whole 
supply.  In  eighteen  hundred  years  the  decrease  in  the 
amount  would  be  only  0.1  per  cent. 

Whether  there  has  been  a  decrease  in  the  past  it  is  not 
possible  to  say.  From  many  considerations  it  appears 
probable  that  the  quantity  of  oxygen  in  the  air  will  never 
become  appreciably  reduced. 


14  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

Gases  of  the  normal  atmosphere.  It  was  supposed  until 
a  few  years  ago  that  all  the  essential  facts  concerning  the 
identity  of  the  gases  of  the  atmosphere  were  known,  but  a 
number  of  new  gases  have  recently  been  discovered.  The 
proportion  of  these  new  elements  is  very  small  and  they 
appear  to  have  no  influence  upon  health. 

In  the  open  country,  upon  the  ocean  and  at  all  elevations, 
the  proportion  of  the  leading  constituents  of  unpolluted 
atmosphere  are  nearly  constant.  When  decided  differences 
have  been  reported  it  is  probable  that  they  have  been  due 
more  to  errors  inseparable  from  the  analytical  technique 
than  to  real  inequalities. 

Still,  inasmuch  as  small  differences  frequently  do  occur 
in  cities  and  other  occupied  places,  it  is  desirable  in  study- 
ing a  problem  of  ventilation  to  determine  the  condition  of 
the  surrounding  outside  atmosphere  at  the  time  and  place 
in  question  as  well  as  the  atmosphere  of  the  enclosed  space 
under  consideration. 

To  get  a  general  idea  of  the  principal  constituents  of  the 
free  atmosphere  under  average  conditions,  we  may  accept 
the  figures  adopted  in  a  recent  English  Government  inquiry 
concerning  the  ventilation  of  workshops.1 

According  to  this  authority,  pure  atmospheric  air,  free 
from  aqueous  vapor,  may  be  taken  to  have  the  following 
composition  by  volume. 

Per  Cent 

Oxygen 20.94 

Nitrogen 78.9 

Argon 0.94 

Carbonic  Acid 0.03 

Helium,  Krypton,  Xenon,  Hydrogen,  etc Traces 


100.00 

1  Report    of   a   Parliamentary   Committee   on  the   Ventilation   of 
Factories  and  Workshops,  London,  1902,  p.  93. 


U  N  I  V  E  R  S  !  T  Y 


CHARACTERISTICS  OF   GOOD  AIR  AND  BAD  AIR      15 

Included  in  this  list,  although  not  specifically  mentioned, 
are  gases  of  decomposition,  principally  ammonia  and 
sulphur  compounds,  which,  with  varying  proportions,  are 
probably  always  present  in  minute  amount. 

According  to  Ramsay,1  the  rare  gases  mentioned  in  the 
foregoing  table  and  recently  separated  from  nitrogen  are 
present  to  the  following  extent;  Helium,  1  part  in  245,300 
volumes  of  air;  neon,  1  part  in  80,800;  argon,  1  part  in 
106.8;  krypton,  1  part  in  20,000,000;  xenon,  1  part  in 
170,000,000. 

Many  authorities  doubt  whether  that  active  form  of 
oxygen  called  ozone  actually  exists  in  the  atmosphere, 
notwithstanding  the  popular  belief  in  its  presence  and  the 
fact  that  some  investigators  have  made  systematic  deter- 
minations of  what  they  have  thought  was  ozone  for  many 
years.  On  the  other  hand,  Ramsay  is  of  opinion  that 
peroxide  of  hydrogen,  an  active  gas  resembling  ozone  in 
some  of  its  properties,  is  generally  present  in  very  small 
quantity.  The  presence  of  ozone  or  peroxide  of  hydrogen 
is  not  without  sanitary  significance  in  a  sample  of  air,  for, 
owing  to  their  energetic  oxidizing  properties,  the  presence 
of  either  gas  may  be  taken  to  indicate  the  absence  of 
organic  matters. 

Odors.  Contrary  to  general  belief,  pure  air  is  odorless, 
colorless  and  tasteless.  Many  of  the  odors  noticed  at  the 
seaside  and  in  the  forest  are  due  to  substances  thrown  off 
in  the  growth  and  decay  of  vegetation  and  are  by  no  means 
directly  beneficial  to  health. 

Odors  are  nearly  always  due  to  gases  and  not  to  solid 
particles,  as  is  popularly  supposed.  The  impression  of 
freshness  noticeable  in  the  country  and  after  showers  is 
1  Gases  of  the  Atmosphere,  London,  1905,  p.  257. 


16          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

more  often  due  to  absence  of  odor  than  to  the  presence  of 
it.  Even  the  dirty  air  of  streets  may  seem  sweet  and  fresh 
on  emerging  from  a  badly  ventilated  enclosure. 

The  sense  of  smell  differs  greatly  among  different  persons 
and  under  different  circumstances.  Warmth  and  moisture 
favor  the  detection  of  odors. 

To  be  accurate,  what  we  call  smell  is  a  mental  effect  due 
to  the  excitement  of  the  olfactory  nerve  when  suitable 
substances  come  in  contact  with  the  external  cells  to  which 
this  nerve  is  attached  in  the  more  remote  parts  of  the  nasal 
cavity.  Odors  can  be,  and  are,  continually  smelled  through 
the  mouth  as  well  as  through  the  nose,  many  so-called 
flavors  used  in  the  preparation  of  food  being,  in  reality, 
substances  producing  odors  and  not  tastes.  Sensations  of 
taste  originate  hi  the  tongue  and  are  restricted  to  such 
impressions  as  those  of  sweetness  and  sourness,  bitterness 
and  salinity. 

The  first  moment  of  contact  gives  the  most  acute  sensa- 
tion of  smell;  this  sense  rapidly  becomes  blunt  after  con- 
tinued exposure.  To  most  persons  a  subway,  which  at 
first  seems  to  have  an  extremely  strong  and  unpleasant 
odor,  has  no  odor  at  all  after  five  minutes  or  so. 
This  acquired  dullness  toward  one  odor  'may  not 
affect  the  keenness  of  perception  for  others.  It  is 
remarkable  how  soon  persons  get  used  to  the  odors 
which  in  one  way  or  another  they  themselves  produce 
and  object  to  much  less  pronounced  odors  from  other 
sources. 

A  partial  or  total  abolition  of  the  sense  of  smell  may 
occur  as  a  result  of  a  catarrhal  condition  or  the  action  of 
injurious  gases.  It  is  not  uncommon  for  persons  who  live 
in  cities  to  become  very  defective  in  the  acuteness  of  this 
sense. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR       17 

Many  gases  are  detectable  by  smell  when  in  extremely 
dilute  form.  Then  the  odor  of  musk  can  be  detected 
for  many  years  without  any  sensible  loss  in  weight. 

It  is  doubtless  chiefly  in  their  power  of  suggestion 
that  certain  odors  of  the  atmosphere  appear  to  be 
beneficial.  And  we  may  say  on  the  converse  side  of  this 
proposition  that  odors  which  are  unpleasant  are  probably 
harmful  only  because  of  the  unpleasant  mental  impressions 
which  they  create.  No  other  sense  is  capable  of  calling 
up  such  vivid  mental  pictures  as  does  the  sense  of 
smell.  Probably  no  sense  is  so  capable  of  leading  one 
astray. 

Carbon  dioxide.  Aside  from  oxygen,  the  two  gases 
which  are  of  greatest  interest  in  studies  of  ventilation  are 
carbon  dioxide  and  water  vapor.  No  other  normal  gases 
of  the  atmosphere  vary  so  much  as  do  these  two  and  none, 
under  ordinary  circumstances,  has  such  an  effect  upon 
comfort. 

The  peculiar  interest  which  attaches  to  carbon  dioxide 
lies  in  the  fact  that  it  is  a  convenient  measure  of  the  extent 
to  which  air  is  vitiated  by  breathing,  by  lights  and  by  fires. 
It  is  a  product  of  respiration  and  of  the  combustion  of 
fuel  and  at  the  same  time  varies  little  in  uncontaminated 
air.  There  appears  to  be  little  difference  between  the 
amount  present  in  pure  country  air,  whether  in  forests  or 
over  the  ocean. 

From  accurate  analyses  made  in  France  by  Reiset 1  who 
used  samples  of  air  measuring  525  liters  each,  2.96  volumes 
of  carbon  dioxide  per  10,000  volumes  of  air  appears  to  be 
close  to  the  normal  for  the  country.  Angus  Smith  reported 
that  the  air  among  the  Scotch  hills  contained  3.36;  J.  S. 

1  Annales  de  Chimie  et  de  Physique,  Vol.  26,  1882,  p.  198. 


18  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

and  E.  S.  Haldane,1  3.0,  and  G.  F.Armstrong,  3.13  for  the 
country  air  of  Scotland.  Three  parts  may  be  accepted  as 
sufficiently  correct  for  most  purposes. 

Water  vapor.  Water  vapor,  not  to  be  confounded 
with  moisture  in  visible  form  to  which  the  term  vapor 
is  so  often  applied,  is  always  present  in  a  normal  atmos- 
phere. 

It  is  usual  to  refer  to  the  presence  of  water  vapor  as 
humidity  and  to  the  ratio  of  the  quantity  present  to  the 
maximum  quantity  which  could  be  present  at  a  given 
temperature  as  the  precentage  of  relative  humidity.  Close 
to  the  ocean  the  relative  humidity  is  generally  in  the 
neighborhood  of  90  per  cent,  but  in  very  dry  places  it  may 
go  below  10  per  cent. 

When  there  is  present  all  the  Water  vapor  which  is 
possible,  the  air  is  commonly  said  to  be  saturated,  a  phrase 
which  some  meteorologists  object  to  on  the  ground  of 
literal  inaccuracy.  It  would  be  more  scientific  to  say  that 
the  space  under  consideration  is  saturated,  for  if  any 
additional  evaporation  should  take  place  into  it  some  of 
the  vapor  already  existing  would  have  to  return  to  the 
liquid  state.  But  it  is  customary  in  this,  as  in  some  other 
directions,  to  employ  the  term  which  is  generally  under- 
stood rather  than  to  insist  upon  excessive  accuracy. 
Saturation  of  the  air  is  a  sufficiently  correct  expression  for 
popular  purposes. 

One  of  the  most  important  facts  to  remember  concerning 
the  existence  of  water  vapor  in  the  atmosphere  is  that  the 
greatest  amount  possible  varies  decidedly  with  the  tempera- 
ture. While  at  0  degrees  Fahrenheit,  the  greatest  possible 
weight  of  a  cubic  foot  of  vapor  is  0.54  grain,  or  35  milligrams, 
1  Physiological  Magazine,  1890,  p.  306. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR       19 

at  80  degrees  Fahrenheit,  the  maximum  is  10.95  grains,  or 
709.56  milligrams. 

The  absolute  humidity  is  the  actual  amount  of  vapor 
present  expressed  either  in  terms  of  its  weight  in  a  given 
volume  of  air  or  in  terms  of  its  expansive  force.  This 
expansive  force  is  often  called  vapor  tension.  Its  amount 
can  easily  be  calculated  when  the  relative  or  absolute 
humidity,  temperature  and  pressure  are  known. 

The  dew  point  is  the  temperature  at  which  condensation 
begins.  It  is  simply  a  convenient  way  of  expressing  the 
amount  of  vapor  present. 

Optimum  conditions  of  moisture,  cold  and  heat.  The 
physiological  effects  of  moisture  have  much  to  do  with 
health.  They  control  the  functions  of  the  skin  and  so 
affect  other  important  organs  of  the  body.  According  to 
the  amount  of  vapor  present  in  the  air,  the  skin  gives  off 
more  or  less  moisture,  and,  owing  to  this  evaporation,  more 
or  less  heat.  When  the  air  is  humid,  a  hot  atmosphere  is 
most  oppressive.  If  the  air  is  cold  and  damp  the  heat  of 
the  body  is  abstracted  rapidly  from  the  exposed  surfaces, 
and  we  feel  chilled.  Dry  air  is  generally  the  most  healthful 
and  comfortable  at  every  temperature.  Draughts  and 
winds  produce  cooling  effects  by  hastening  evaporation, 
by  forcing  warm  air  out  of  our  clothes  and  by  abstracting 
heat  by  conduction. 

At  a  temperature  of  60  degrees  Fahrenheit,  when  suit- 
ably clothed  and  not  working  too  hard,  we  feel  comfortable 
in  an  atmosphere  saturated  with  watery  vapor,  that  is, 
while  rain  is  falling,  but  from  the  moment  the  temperature 
rises  so  that  refrigeration  by  the  rapid  evaporation  of  sweat 
from  the  surface  of  the  body  becomes  necessary  to  preserve 
the  normal  body  temperature  of  98  degrees,  we  become 


20          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

uncomfortable.  If  the  temperature  falls  much  below  65 
degrees,  we  feel  cold,  unless  we  exercise.  The  most  com- 
fortable temperature  in  which  to  remain  without  exercise 
is  between  65  and  70  degrees. 

All  things  considered,  cold  weather  is  better  than  hot 
weather  for  the  average  person,  for,  since  more  heat  is  lost 
from  the  body  in  cold  weather,  the  production  of  heat  must 
be  increased  and  this  means  more  active  metabolism  and 
probably  greater  activity  of  all  the  tissues  of  the  body. 
This  stirring  up  of  the  vital  powers  is  thought  by  many 
persons  to  account  in  large  measure  for  the  greater  vigor 
of  northern,  as  compared  with  southern,  people.  It  is 
even  believed  by  some  to  increase  personal  resistance 
to  disease. 

Rapid  and  decided  changes  in  temperature  are  universally 
considered  dangerous,  particularly  when  the  temperature 
is  falling  below  60-65  degrees. 

Dust.  The  atmosphere  over  both  land  and  sea  normally 
contains  solid  matters  in  the  form  of  dust,  but  in  uncon- 
taminated  air  the  amount  is  usually  very  small  and  the 
particles  exceedingly  minute.  These  particles  are  raised 
by  winds  from  the  earth  as  dust  and  from  the  waves  of  the 
ocean  as  fine  droplets,  the  water  of  which  evaporates, 
leaving  the  mineral  matters  in  solid  form. 

Under  the  microscope,  dust  from  the  air  in  the  country 
has  been  found  to  contain  particles  of  wood  fibre,  frag- 
ments of  plants,  bits  of  animal  hairs  and  feathers,  silica, 
clay,  and,  in  fact,  remains  of  nearly  every  living  and 
inorganic  thing  which  is  to  be  found  on  the  earth's 
surface. 

Sea  air  has  been  found  to  contain  minute  quantities  of 
iodine,  possibly  in  organic  combination,  and  due  probably 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR       21 

to  minute  organisms  or  fragments  of  once  living  animals 
and  plants  from  the  sea. 

In  quiet  air  solid  matters  settle  toward  the  earth,  but 
there  is,  apparently,  no  limit  to  the  length  of  time  that  the 
finest  particles  of  solid  matter  may  remain  suspended  in 
the  moving  atmosphere;  the  period  certainly  covers  months 
and  probably  years. 

The  dust  from  some  volcanic  eruptions  has  been  known 
to  encircle  the  earth.  Sand,  raised  by  wind  storms  on  the 
Desert  of  Sahara,  is  sometimes  carried  across  the  Medi- 
terranean Sea  and  deposited  in  the  Islands  of  Malta,  in 
Sicily,  and  even  in  the  South  of  France. 

While  it  is  probable  that  the  dust  normally  present  in 
good  country  air  does  not  appreciably  injure  health, 
excessive  amounts  of  some  dusts,  such  as  that  from  the 
Sahara,  affect  the  mucous  membranes  and  produce  symp- 
toms strongly  resembling  some  of  those  which  are  charac- 
teristic of  influenza. 

The  ultra-microscopic  dust  contained  in  the  upper  air 
of  the  open  country  is  an  important  ingredient  of  the 
atmosphere  when  considered  from  a  climatalogical  stand- 
point, for  it  exercises  an  influence  upon  the  temperature  of 
the  air,  probably  determines  its  color  and  the  illuminating 
effect  produced  by  the  sun  upon  the  sky.  With  absolutely 
no  dust  in  the  atmosphere  there  would  be  no  clouds,  no 
twilight  and  no  rain.  By  furnishing  nuclei,  the  fine  dust 
of  the  atmosphere  permits  water  vapor  to  condense  and 
form  particles  of  moisture  which  result  in  fog,  mist  and 
rain. 

The  number  of  these  ultra-microscopic  dust  particles  in 
the  free  air  of  country  and  sea,  as  well  as  in  the  air  of 
cities,  has  been  made  the  subject  of  careful  study  by 
Ait  ken  and  others.  Ait  ken's  observations  led  him  to 


22          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

estimate  that  one  cubic  inch  of  air  in  the  open  country 
contained  2000  dust  particles;  in  a  city  3,000,000  and  in 
enclosed  spaces  occupied  by  human  beings  30,000,000.! 
Most  of  these  particles  are  ultra-microscopic. 

Forms  of  life.  Finally,  as  ingredients  of  normal  air, 
must  be  mentioned  particles  of  organized  matter,  some 
of  which  are  living,  others  existing  in  a  resting  stage  and 
still  others  dead.  The  most  interesting  of  these  are  the 
minute  forms  of  life  which  are  almost  everywhere  present 
in  the  atmosphere  and  collectively  termed  microorganisms. 
They  include  bacteria,  yeasts  and  molds. 

By  far  the  most  important  of  these  living  particles,  from 
a  physiological  standpoint,  are  the  bacteria.  Bacteria  of 
some  kinds  are  almost  everywhere  present  in  the  atmos- 
phere. The  kinds  which  are  popularly  called  disease 
germs  are  exceedingly  rare  except  in  the  vicinity  of  living 
beings. 

Mere  numbers  of  bacteria  are  generally  considered  by 
sanitarians  to  be  of  little  significance.  Yet  very  large  num- 
bers are  always  present  in  the  air  of  unhealthy  places, 
while  small  numbers  generally  occur  where  the  air  is  pure. 
It  is  difficult  to  place  a  limit  to  the  number  which  may  be 
present  in  air  without  causing  it  to  be  regarded  as  impure. 
Some  authorities,  as  Fliigge,  for  example,  have  suggested 
100  per  cubic  meter  as  a  fair  standard. 

Unlike  dust  particles  with  which  they  are  often  associated 
in  air  near  land,  bacteria  are  found  only  rarely  in  the 
atmosphere  over  the  ocean  and  on  mountain  tops. 

The  sea  and,  in  fact,  all  wet  or  moist  surfaces,  as  well  as 

1  Nature,  Vol.  31,  p.  265,  Vol.  41,  p.  394.  See  also  "  Cloudy  Con- 
densation," by  John  Aitken,  F.R.S.,  Proc.  Roy.  Soc.  Lond.,Vol.  21, 
pp.  403-439.  Also  Smithsonian  Reports,  1893. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      23 

rain  and  snow,  perform  a  useful  service  in  removing  solid 
matters  from  the  atmosphere.  Contrary  to  the  popular 
idea,  there  are  fewer  bacteria  in  the  air  when  the  ground  is 
wet  with  slush  and  snow  than  when  it  is  dry.  Once  in 
contact,  dust  and  bacteria  become  instantly  attached  to 
whatever  is  wet  and  do  not  leave  such  surfaces  unless 
driven  away  by  spraying  or  splashing.  This  is  an  impor- 
tant fact;  it  accounts  for  the  observation  that  ordinary 
air  from  the  mouth  and  nose  does  not  contain  bacteria, 
while  the  invisible  droplets  given  off  in  sneezing,  coughing, 
spitting  and  speaking  always  contain  large  numbers  of 
them. 

Among  natural  conditions  which  destroy  bacteria  are 
(a)  Sunlight :  Sunlight  destroys  most  bacteria  better  than 
many  artificial  disinfectants;  (6)  Drying:  Although  the 
germs  of  tuberculosis  and  of  some  other  diseases  withstand 
drying  for  months,  most  germs  cannot  live  without  mois- 
ture; (c)  Air  Currents  and  Gravity:  These  are  useful 
in  so  far  as  they  transport  bacteria  to  places  where  they 
are  destroyed. 

Practically  no  microorganisms  which  grow  and  multiply 
in  nature  apart  from  human  life  are  dangerous  to  breathe, 
although  certain  molds  and  bacteria  grow  outside  of  the 
human  body  under  conditions  which  have  led  some  persons 
to  conclude  that  they  are  natural  enemies  to  the  human  race. 

Bacteria  are  divisible  into  two  great  classes:  (1)  The 
Saprophytes:  These  live  on  dead  organic  matter  and  (2) 
The  Parasites:  These  live  within,  or  upon,  a  living  host. 
Some  belong  to  both  classes  but  show  a  distinct  preference 
for  one  form  of  existence  or  the  other.  The  various 
species  of  these  two  groups  are  believed  to  number  thou- 
sands and  each  is  as  separate  and  immutable  as  are  the 
separate  species  among  larger  plants. 


24          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

THE  AIR  OF  TOWNS  AND  CITIES 

It  is  a  well  known  fact  that  the  air  of  cities  always  differs 
somewhat  in  composition  from  the  normal  atmosphere 
of  the  country.  The  great  consumption  of  fuel  and  the 
production  of  innumerable  gases  and  dusts  from  industrial 
establishments  give  to  some  cities  an  atmosphere  which  is 
unmistakably  unlike  that  of  the  neighboring  country. 

Air  of  London,  Paris  and  New  York.  London  is  probably 
the  most  conspicuous  example  of  a  city  which  modifies  its 
own  climate.  Repeated  investigation  shows  that  the  air 
of  London  contains  more  carbon  dioxide  than  uncon- 
taminated  country  air,  very  much  more  dust  and  more 
microorganisms.  There  is,  moreover,  much  less  sunlight 
and  a  more  even  temperature  in  London  than  occur  outside 
of  the  city  limits.  The  frequency  and  density  of  the  fogs 
which  characterize  the  city  are  largely  due  to  the  smoke 
produced;  this  fog,  acting  like  a  blanket,  keeps  out  sun- 
light and  air. 

Angus  Smith,  who  found  3.01  volumes  of  carbon  dioxide 
per  10,000  in  the  parks  of  London,  found  3.80  in  the  streets. 
His  average  of  35  analyses  of  samples  from  different  parts 
of  London  was  4.39.  The  same  investigator  reported  4.03 
for  the  air  of  Manchester,  4.14  for  the  air  of  Perth  and  5.02 
for  Glasgow. 

The  most  careful,  long  series  of  analyses  of  London  air 
yet  made  were  carried  out  by  Russel  who,  as  a  result  of  159 
determinations,  announced  4.03  as  the  average  from  the 
center  of  London.  Butterfield,  who  was  instructed  by  a 
committee  of  the  House  of  Commons  to  determine  as 
nearly  as  present  scientific  methods  would  allow,  the 
condition  of  the  air  in  the  debating  chamber  of  the  House, 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR       25 

when  in  use,  found  the  outside  air  of  London  contained  3.37 
parts  of  carbon  dioxide,  with  a  maximum  of  3.64. 

The  municipal  laboratory  of  Paris  1  has  kept  records  of 
the  amount  of  carbon  dioxide  in  the  air  of  Paris  since  1890 
with  results  which  have  been  published  in  the  official 
journal  of  the  Montsouris  Laboratory.  In  the  center  of 
Paris  the  annual  average  has  been  slightly  higher  than  in 
the  southern  part.  In  the  center  it  has  varied  from  3.06 
to  3.44.  In  the  south  the  minimum  has  been  the  same  as 
in  the  center,  but  the  maximum  has  not  been  so  high. 
The  monthly  range  has  been  3.04  to  3.36  in  the  center.  In 
both  sections  the  greatest  amount  has  occurred  in  Novem- 
ber and  the  least  in  July. 

For  ten  years  from  1891  to  1900,  analyses  were  made 
by  the  Montsouris  Laboratory  to  determine  to  what  extent 
the  carbon  dioxide  varied  during  the  day  and  night.  Six 
samples  were  analyzed  each  day  between  6  A.M.  and  6 
P.M.  and  six  between  6  P.M.  and  6  A.M.  The  results 
showed  very  slight  differences  in  the  southern  part  of  the 
city,  but  there  was  much  less  uniformity  in  the  central 
part.  The  figures  follow: 

Carbon  dioxide  in  the  air  of  Paris  during  the  day  and 
night,  1891-1900,  inclusive. 


Montsouris  Park 

Center  of  City 

Day  

3  10 

3  34 

Night    

3.18 

3  21 

24  hours,  average      .    .           . 

3  14 

3  27 

In  the  observations  made  by  the  author  for  the  Rapid 
Transit  Commission  of  New  York  and  recorded  graphically 
1  Annales  de  TObservatoire  de  Paris,  VI.,  1905,  p.  322. 


26          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

elsewhere  in  this  volume  the  amount  of  carbon  dioxide  was 
found  to  vary  from  hour  to  hour  in  the  air  of  the  streets  of 
New  York  very  much  as  it  varied  in  the  air  of  the  subway. 
It  was  highest  at  6  P.M.  and  lowest  between  1.30  and  3 
A.M.,  with  certain  fluctuations  through  the  day.  The 
average  of  309  analyses  was  3.67. 

Unwholesome  gases.  The  gases  from  coal  produce  an 
amount  of  pollution  which  should  not  be  overlooked.  The 
quantity  of  coal  consumed  and  the  volume  of  offensive 
gases  given  off  in  the  large  cities  is  very  great.  In  New 
York,  in  1905,  it  was  estimated  that  9,000,000  tons  of 
anthracite  and  6,500,000  tons  of  bituminous,  or  a  total  of 
15,500,000  tons  of  coal  were  burned.  Of  this  amount 
Manhattan  Island  probably  used  nearly  one-half.  This 
coal  produced  in  burning  about  3,000  tons  of  sulphuric 
acid  and  75,000  tons  of  carbon  dioxide  per  day.  The 
heat  from  this  coal  was  sufficient  to  have  raised  and  kept 
raised  the  temperature  of  the  air  over  the  whole  area  of 
the  city.  If  these  gases  were  not  carried  away  by  the 
winds,  but  became  mixed  with  the  air  of  the  streets  and 
buildings,  the  atmosphere  would  have  become  so  poisonous 
as  to  kill  all  the  inhabitants. 

The  atmosphere  of  cities  and  towns  where  manufactories 
exist  is  often  contaminated  with  unwholesome  gases  of 
industrial  origin.  Among  the  gases  given  off  from  indus- 
tries common  in  large  cities  are  the  following  given  by 
Notter.1 

Hydrochloric  acid  from  alkali  works;  sulphurous  acid 
and  sulphuric  acid  from  copper  works  and  bleaching 
operations;  sulphuretted  hydrogen  from  chemical  works, 
especially  those  which  produce  ammonia;  carbon  monoxide 

1  Theory  and  Practice  of  Hygiene,  2d  Ed.,  1900,  p.  155. 


CHARACTERISTICS  OF   GOOD  AIR  AND  BAD   AIR      27 

from  iron  furnaces  —  this  may  amount  to  from  22  to  25 
per  cent,  and  from  copper  furnaces  from  15  to  19  per  cent; 
organic  vapors  from  glue  refineries ;  bone  burners ;  slaughter 
houses,  knackeries;  zinc  fumes  from  brass  foundries; 
arsenical  fumes  from  copper  smelting;  phosphoric  fumes 
from  the  manufacture  of  matches;  and  carbon  disulphide 
from  some  India  rubber  works. 

The  actual  weight  of  volatile  matters  thrown  into  the 
air  by  manufactories  is  often  very  great.  The  following 
results  of  analysis  of  flue  gases  of  a  large  smelter  are  given 
by  Harkins  and  Swain.1 

Average  in  pounds  per  day  of  substances  thrown  off  in 
the  smoke  of  a  large  American  smelter. 

Arsenic  trioxide 59,270 

Antimony  trioxide 4,320 

Copper 4,340 

Lead      4,775 

Zinc 6,090 

Oxides  of  iron  and  aluminium 17,840 

Bismuth 880 

Manganese 180 

Silica 10,260 

Sulphur  trioxide 447,600 

Sulphur  dioxide 4,636,000 

It  cannot  be  doubted  that  many  of  the  gaseous  products 
of  factories  are  injurious  to  health  although  it  is  true  that, 
unless  favored  by  particular  conditions  of  wind  and  weather, 
they  are  not  noticed  by  persons  at  more  than  a  very  short 
distance  from  the  factories  where  they  are  produced. 
Most  of  these  gases  are  well  known  to  be  injurious  if  present 
in  appreciable  quantity. 

The  following  table 2  has  been  compiled  from  the  reports 
of  many  investigators  to  show  at  what  concentrations 

1  Journal  Am.  Chem.  Soc.,  Vol.  29.,  No.  7,  p.  970. 
a  Lehmann,  Meth.  Prac.  Hy.,  1901,  p.  174. 


28 


THE  AIR  AND  VENTILATION   OF  SUBWAYS 


various  common  industrial  gases  are  capable  of  producing 
immediate  and  observable  effects  upon  health. 

Table  showing  concentration  by  volume  at  which  certain 
common  gases  cause  visible  injury  to  health. 


Rapid  and 

Bearable  for 

Trifling  symp- 

Name of 

Gas 

dangerous 
injury 

30-60  min. 
without  grave 

toms  after 
action  for 

effects 

some  hrs. 

Hydrochloric  acid 

.  per  1000    . 

1  .  5  to  2 

.051 

.01 

Sulphurous  acid    . 

.   per  1000    . 

0.4  to  5 

.05 

Carbonic  acid     .    . 

.  per  cent    . 

About  30 

6  to  8 

1  to  2 

Ammonia     .    . 

per  1000 

2  .  5  to  4  .  5 

0  3 

.1 

Chlorine  bromine. 

.  per  1000   . 

.04  to  .06 

.004 

.001 

Iodine  

per  1000   . 

.003 

.005  to  .001 

Hydrogen  sulphide 

.   per  1000   . 

0.5to0.7 

.2  to  .3 

.1  to  .15 

Carbon  disulphide 

.  per  1000   . 

.01 

.002 

.001 

Carbon  monoxide 

.  per  1000    . 

2  to  3 

.  5  to  1.0 

.2 

Composition  of  city  dusts.  Beside  the  carbon  from  smoke 
the  dust  of  cities  is  composed  of  particles  of  nearly  every 
conceivable  substance  which  is  capable  of  being  ground 
into  a  finely  divided  condition  by  wear  and  tear  amid  the 
innumerable  activities  of  the  people. 

Little  care  is  taken  to  prevent  dust  from  polluting  the 
atmosphere.  Carpets  and  rugs  are  shaken  on  housetops, 
sweepings  are  thrown  from  windows,  and  dust  composed 
largely  of  horse  manure,  lies  in  windrows  on  sidewalks  and 
roadways.  In  nearly  every  large  city  there  are  factories 
in  which  large  quantities  of  harmful  dusts  are  produced 
and  which  are  provided  with  blowers  to  force  the  injurious 
particles  into  the  air  of  the  streets.  Building  operations, 
overloaded  coal  and  refuse  carts,  push  carts  and  horses 
also  contribute  largely  to  the  production  of  city  dust. 

On  approaching  New  York  from  the  ocean,  a  low,  dense 

1  max.  0.1. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      29 

haze  can  distinctly  be  seen  hanging  over  the  city,  and  on 
passing  in  and  out  of  the  harbor  a  decided  difference  in  the 
odor  of  the  air  may  be  detected.  No  analyses  are  needed 
to  show  that  there  are  impurities  in  this  atmosphere.  The 
haze  is  largely  composed  of  particles  of  soot  from  imper- 
fectly consumed  coal  and  solid  matters  from  the  factories 
and  streets  of  the  metropolis  and  cities  in  its  vicinity. 

Bacteria  are  vastly  more  numerous  in  the  air  of  cities 
than  in  the  atmosphere  of  the  open  country.  While 
Miquel  found,  as  a  result  of  six  years  of  observation,  an 
average  of  455  per  cubic  meter  in  the  air  of  Montsouris 
Park,  in  the  south  of  Paris,  he  found  nearly  4000  in  the  air  of 
the  busy  center  of  the  city.  The  numbers  found  may  reach 
almost  any  figure,  depending  upon  local  circumstances. 

Among  the  worst  ingredients  of  city  dust  are  the  parasitic 
bacteria.  The  most  harmful  are  produced  by  the  human 
body  in  disease  and  are  given  off  in  excretions  of  the  lungs, 
throat,  mouth  and  nose.  Most  of  these  bacteria  die  soon 
after  leaving  the  body,  but  some  resist  drying  and,  being 
cast  into  the  streets,  eventually  become  desiccated,  ground 
into  powder  and  distributed  through  the  air  to  be  breathed 
with  dust  particles.  Rarely,  if  ever,  do  the  germs  of 
common  diseases  grow  in  the  dust  and  dirt  of  a  city, 
much  less  originate  there.  The  enormous  numbers  of 
harmful  germs  cast  off  by  sick  persons  and  convalescents 
are  sufficient  to  make  dust  potentially  dangerous  wher- 
ever filth  abounds,  ventilation  is  inadequate  or  crowding 
excessive. 

Effects  of  atmospheric  impurities  in  cities.  The  smoke 
in  the  atmosphere  of  cities  has  been  found  to  be  injurious 
to  plants,  metal  and  stone.  It  blackens  the  lungs  of  all 
who  breathe  it. 


30  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

The  carbon,  of  which  the  smoke  particles  are  chiefly 
composed,  closes  up  the  pores  of  the  leaves  of  plants  and 
interferes  with  their  functions,  especially  the  transpiration 
of  water  vapor  and  of  air.  Were  it  not  for  the  fact  that  the 
breathing  apparatus  lies  on  the  under  side  of  the  leaves 
where  it  is,  in  a  measure,  protected,  it  would  be  impossible 
for  some  trees  to  live  in  cities,  so  covered  with  carbon  do 
they  become.  In  fact  the  conifers,  which  do  not  change 
their  leaves  as  often  as  do  other  plants,  actually  smother 
with  dirt,  as  pointed  out  by  Agar  and  others.1 

Besides  the  mechanical  injury  produced  by  the  soot,  the 
sulphurous  gases  from  coal  are  harmful  chemically.  It  has 
been  shown  by  several  investigators  that  the  sulphur  from 
flue  gases  is  highly  injurious  to  plants.  In  one  case  reported 
by  Hay  wood  2  vegetation  was  injured  for  22  miles  from  a 
large  copper  smelter.  In  numerous  instances  the  ground 
surrounding  such  works  is  entirely  stripped  of  vegetation. 
Unfortunately  there  is  no  simple  and  exact  method  of 
detecting  small  quantities  of  sulphur  dioxide  in  the  air. 
By  drawing  air  through  peroxide  of  hydrogen,  Oliver  found 
the  sulphur  dioxide  in  London  air  to  range  between  1.5  mg. 
to  14.1  mg.  per  cubic  meter  of  air  or  from  1.17  to  8.73 
parts  per  million. 

Not  only  have  trees  and  other  vegetation  been  destroyed 
by  gases  from  industrial  works,  but  cattle  have  been  killed 
by  feeding  on  forage  contaminated  in  this  way.  The 
difficulty  here  was  from  mineral  poisons.  From  tabulated 
results  of  analyses  of  fodder  given  by  Hay  wood,  it  appears 
that  for  herbivorous  animals  to  exist  within  several  miles 
of  certain  American  smelters,  they  must  become  confirmed 
arsenic  eaters,  with  a  capacity  of  from  3  to  10.9  grains  of 

1  Journal  of  the  Royal  Sanitary  Institute,  Vol.  27,  1906,  p.  173. 

2  Journal  Am.  Chem.  Soc.,  Vol.  29,  No.  7,  p.  998. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD   AIR      31 

arsenic  per  day.  At  autopsy  there  is  no  difficulty  in 
discerning  the  injuries  produced.  The  gastro-intestinal 
tract  is  inflamed,  as  is  the  mucous  membrane  of  the  upper 
air  passages.  The  glands  of  the  stomach  and  kidney  in 
section  show  desquamation,  cloudy  swelling  and  fatty 
degeneration.  The  effects  of  these  fumes  upon  the  health 
of  human  beings  must  also  be  injurious. 

Because  of  the  sulphurous  and  sulphuric  acids  which  are 
present  in  city  air,  the  rain  water  of  cities  has  a  decided 
effect  upon  stone  and  iron.  Rideal 1  found  coal  soot  from 
several  different  cities  to  contain  the  following  percentages 
of  SO,: 

London 4.6 

Manchester 4.3 

Glasgow 7.9 

Dust  collected  from  20  square  yards  of  glass  roof  at  the 
botanical  gardens  of  Kew  and  Chelsea  contained  5  per 
cent  of  sulphurous  acid. 

In  New  York  City  a  peculiar  yellow  hue  soon  settles  upon 
buildings  constructed  of  white  marble  or  other  light- 
colored  material,  and  the  author's  investigations  show  that 
this  color  is  largely  due  to  dust  containing  iron,  acted  upon 
by  the  moisture  of  the  atmosphere.  Calculations  based 
on  the  consumption  of  horse-shoes,  tires  of  vehicles,  and  the 
brakes,  rails  and  machinery  of  street  and  elevated  cars 
show  that  the  amount  of  iron  and  steel  ground  up  every 
day  in  the  heavy  and  congested  traffic  of  New  York  is 
enormous. 

The  effects  upon  human  beings  of  breathing  city  dust 
have  repeatedly  been  described  by  sanitary  authorities 
and  the  principal  facts  with  relation  to  this  matter  are 

1  Journal  of  the  Royal  Sanitary  Institute,  Vol.  27,  1906,  pp.  76-77. 


32          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

now  considered  to  be  beyond  the  range  of  speculation  or 
hypothesis.1 

The  effects  of  city  dust  are  most  apparent  in  the  respira- 
tory apparatus,  although  it  may  produce  injury  to  the  eyes 
and  skin.  Most  of  the  particles  breathed  in  are  caught  by 
the  mucous  membranes  of  the  throat  and  nose.  In  view 
of  the  delicacy  of  these  structures,  the  burden  which  they 
are  capable  of  withstanding  seems  enormous,  but  there  is 
a  limit  beyond  which  even  their  wonderful  toleration 
ceases.  Nearly  every  city  dweller  suffers  continually  to 
a  greater  or  less  extent  with  chronic  catarrhal  or  other 
inflammation  of  the  nose  or  throat,  not  to  mention  more 
serious  affections. 

Frequency  of  disease  due  to  infected  air.  It  may  be 
asked,  if  the  germs  of  disease  are  so  common  why  is  it  that 
great  epidemics  do  not  take  place?  As  a  matter  of  fact, 
great  epidemics  do  take  place,  but  the  diseases  which  they 
carry  are  so  common  that  they  do  not  attract  attention. 
Nor  are  they  always  mild  diseases.  The  annual  average 
number  of  deaths  from  diseases  of  the  respiratory  system 
in  the  registration  cities  of  the  United  States  was,  accord- 
ing to  the  last  government  census,  in  the  five  years,  1900- 
1904,  464,  while  that  of  smallpox  was  4.6. 

THE  AIR  OF  CONFINED  SPACES 

Composition  of  respired  air.  The  difference  between 
the  principal  gases  in  inspired  and  expired  air  is  given  by 
the  following  table  taken  from  Foster.2 

1  Prudden  —  Clean  Air,  Medical  Record,  Feb.  3,  1906. 

2  Foster's  Text  Book  of  Physiology,  N.  Y.,  Edition  published  in 
1906,  pp.  440^42. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      33 


Inspired  air 

Expired  air 

Oxygen 

20.81 

16.003 

Nitrogen                     .... 

79.15 

79.589 

Carbon  dioxide     

.04 

4.38 

From  these  figures  it  appears  that  there  is  little  change 
in  the  nitrogen,  but  that  the  oxygen  has  been  reduced 
about  4  per  cent  and  carbon  dioxide  increased  by  nearly 
the  same  amount. 

Beside  carbon  dioxide,  expired  breath  contains  about  5 
per  cent  of  aqueous  vapor  and  various  other  gases,  including 
slight  amounts  of  ammonia,  hydrogen  and  marsh  gas. 
These  are  of  little  or  no  direct  consequence  in  studies  of 
ventilation. 

The  average  adult  takes  into  his  lungs  about  396  cubic 
inches  or  6500  c.c.  of  air  per  minute  and  gives  off  the  same 
amount  of  vitiated  air  which  must  be  greatly  diluted  before 
it  is  generally  considered  suitable  for  further  respiration. 
This  is  not  saying  that  the  carbon  dioxide,  itself,  is  danger- 
ous to  breathe  even  for  a  considerable  period  of  time  and  in 
considerable  concentration.  It  must  be  present  to  an 
extent  40  times  that  present  when  a  room  begins  to  smell 
stuffy  and  unpleasant  before  it  produces  any  immediate 
effect  and  then  there  is  merely  an  increase  in  the  rate  of 
breathing.  Neither  does  an  increase  or  decrease  of  2  or  3 
per  cent  in  the  oxygen  seem  to  produce  any  evil  effect. 
Long  before  the  air  becomes  so  vitiated  as  this,  however, 
other  impurities  from  the  lungs  make  the  air  extremely 
unpleasant.  Under  ordinary  circumstances  the  carbon 
dioxide  in  badly  vitiated  places  seldom  rises  above  50 
parts  per  10,000. 


34  THE  AIR  AND   VENTILATION  OF  SUBWAYS 

The  measure  of  dilution  necessary  to  keep  air  free  from 
odors  due  to  the  presence  of  people  is  very  easily  understood, 
for  we  know  that  while  fresh  air  contains  about  .03  per  cent 
of  carbon  dioxide,  and  air  which  has  passed  through  the 
lungs  about  4.41  per  cent,  the  air  of  enclosed  spaces  becomes 
uncomfortably  close  and  musty  when  the  carbon  dioxide 
exceeds  .08  per  cent;  this  is  about  5  parts  per  10,000  above 
the  amount  in  good  outside  air. 

It  should  be  remembered  that  the  odor  does  not  depend 
on  the  amount  of  carbon  dioxide ;  this  gas  has  no  odor  and 
is  only  an  indicator  of  respiratory  impurity.  The  temper- 
ature and  the  amount  of  moisture  present  contribute  to  an 
important  extent  in  making  the  impure  character  of  air 
apparent.  The  higher  the  temperature  and  the  greater 
the  humidity  the  more  noticeable  the  odor  becomes. 
DeChaumont  concluded  that  an  increase  of  humidity  of 
1  per  cent  has  as  much  influence  on  the  sense  of  smell  as 
a  rise  of  4.18  degrees  of  temperature. 

Cause  of  unpleasant  odors.  The  unpleasant  odors  of 
poorly  ventilated  places  are  due  to  many  causes.  Nearly 
every  substance  which  exists  possesses  a  characteristic 
odor  and  if  no  odor  is  noticeable  in  a  room  or  other  enclosed 
space  it  is  because  the  odors  are  very  delicate,  or  we  have 
become  accustomed  to  them,  or  the  ventilation  is  sufficient 
to  dilute  them  to  a  point  beyond  which  they  can  no  longer 
give  us  any  sensation. 

Among  the  most  familiar  odors  of  poorly  ventilated 
places  are  those  of  gas  lights,  oil  lamps,  food,  clothing  and 
personal  odors.  The  cause  of  the  nauseous  odors  of 
human  origin  which  commonly  exist  in  jails,  railroad  cars 
and  other  places  of  assembly  have  been  the  subject  of 
frequent  investigation  and  speculation.  The  opinion  of 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      35 

Billings,  Mitchell  and  Bergey,1  and  several  others  is 
that  they  are  due  to  volatile  fatty  acids  associated  with 
bodily  excretions  and  products  of  decomposition  con- 
tained in  the  expired  breath  of  persons  having  decayed 
teeth,  foul  mouths  or  certain  disorders  of  the  digestive 
apparatus. 

It  was  once  commonly  believed  that  expired  air  contained 
organic  matter  of  a  toxic  nature  and  experiments  were 
made  which  seemed  to  show  that  when  the  fluid  which  can 
be  condensed  from  the  moisture  of  the  breath  is  injected 
into  animals,  it  produces  death.  Some  doubt,  however, 
has  recently  been  attached  to  the  accuracy  with  which  these 
experiments  were  made,  the  present  trend  of  opinion 
being  that  so  far  as  gaseous,  organic  impurities  are  con- 
cerned, air  can  be  breathed  over  and  over  again  without 
serious  physiological  effects. 

Amount  of  carbon  dioxide  produced  by  human  beings. 
The  amount  of  carbon  dioxide  produced  varies  with  dif- 
ferent people  according  to  their  size  and  activity.  In  their 
studies  of  the  ventilation  of  factories  and  work-shops,  the 
Committee  of  Parliament,  already  mentioned,  considered 
that  one  cubic  foot  per  hour  was  a  probable  average  quan- 
tity produced  by  persons  at  work  in  factories.3 

The  amount  of  carbon  dioxide  produced  depends  upon 
whether  one  is  at  rest  or  at  work,  fasting  or  eating  an 
abundance  of  food ;  it  depends  also  upon  the  nature  of  the 
food,  body  weight  and  age.  According  to  Landois  and 
Rosemann,4  expired  air  contains  a  range  of  from  3.3  to  5.5 

1  Smithsonian  Reports,  July  18,  1905,  p.  389. 

2  First  Report  of  the  Departmental  Committee  on  the  Ventilation 
of  Factories  and  Workshops,  London,  1902,  p.  94. 

8  Lehr.  Physiol.  des  Men.  Berlin,  1905,  llth  Ed.,  p.  229. 


36 


THE  AIR  AND   VENTILATION  OF  SUBWAYS 


per  cent  of  carbon  dioxide  or  an  average  of  4.38  per  cent 
by  volume. 

The  most  accurate  tests  in  this  direction  yet  made  in 
America  have  been  those  reported  by  Atwater  and 
Benedict l  in  connection  with  calorimeter  experiments  at 
Wesleyan  University.  The  following  table  shows  the 
results  which  were  obtained  in  35  tests. 

Amount  of  carbon  dioxide  exhaled  by  men  at  work  and 
at  rest  at  different  hours  of  the  day. 


Rest 

Work 

7a  -IP.    . 

grams 
18  22 

grams 
46  61 

IP  -7P  

17.89 

46  47 

7P  _ia 

16  78 

17  95 

ja  _7a 

10  87 

11  73 

Average  per  hour 

16  11 

30  71 

8198  c  c 

15,628c.c. 

For  practical  purposes  we  may  consider  that  a  man  loads 
500  c.c.  of  air  at  each  breath  to  the  extent  of  about  4  per 
cent  of  carbon  dioxide. 

Value  of  analyses.  The  usefulness  of  analyses  depends 
upon  the  accuracy  with  which  they  are  made  and  inter- 
preted. They  are  reliable  only  when  they  are  performed 
with  suitable  apparatus  and  by  persons  who  have  con- 
siderable skill.  Up  to  the  present,  no  simple  methods 
have  been  devised  which  will  enable  a  person  not  thor- 
oughly trained  to  determine  the  chemical  or  bacteriological 
purity  of  air  without  running  a  large  chance  of  obtaining 
very  misleading  results.  The  usual  tests  are  valueless  in 
inexperienced  hands. 

i  Bull.  136,  U.  S.  Dept.  of  Agri.,  1902,  p.  147. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR       37 

Furthermore,  unless  the  samples  to  be  analyzed  are 
collected  with  great  care  to  insure  that  they  fairly  repre- 
sent the  whole  air  under  consideration,  serious  error  is 
practically  certain  to  result. 

Fortunately  all  errors  made  in  determining  the  amount 
of  carbon  dioxide,  the  most  usual  test  of  the  quality  of 
the  air,  are  on  the  side  of  safety  and  are  unbalanced.  The 
novice  finds  the  air  too  impure  rather  than  too  good.  The 
cumulative  nature  of  the  errors  which  may  occur  in  these 
analyses  undoubtedly  accounts  for  many  of  the  alarming 
reports  which  have  been  printed  concerning  the  air  of 
subways  and  tunnels  based  on  the  work  of  amateur  inves- 
tigators. 

Heat  produced  by  human  beings.  The  amount  of  heat 
given  off  by  the  breath  and  skin  has  been  variously  esti- 
mated by  different  investigators.  According  to  Landois 
and  Rosemann  l  the  average  man  produces  every  24  hours 
per  kilo  of  body  weight  32  to  38  calories  when  at  rest;  35 
to  45  when  in  easy  action  and  50  to  70  when  at  hard  work. 
If  the  average  man  is  assumed  to  weigh  70  kilos  or  154 
pounds,  this  is  equivalent  to  from  2240  to  4900  calories 
per  day. 

Otherwise  about  1399  calories  may  be  assumed  to  be 
given  off  per  square  meter  of  surface.  As  the  average  man 
of  154  pounds  may  be  assumed  to  measure  2.09  square 
meters,  the  number  of  calories  given  off  by  him  per  day  is 
about  2923.  These  estimates  compare  fairly  well  with 
American  figures. 

The  observations  of  Atwater  and  Rosa 2  and  Atwater  and 

1  Lehr.  Physiol.  des  Men.,  Berlin,  1905,  llth  Ed.,  p.  408. 
3  Atwater  and  Rosa,  Bull.  63,  U.  S.  Dept.  Agri. 


38          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

Benedict *  give  the  most  accurate  estimations  yet  made  in 
America  of  the  heat  given  off  by  the  breath  and  skin.  The 
figures  are  somewhat  lower  than  those  just  quoted.  The 
average  of  13  experiments  was  2219  calories  per  24  hours 
for  an  average  man  at  rest,  and,  as  an  average  of  6  experi- 
ments, 3409  calories  for  a  man  at  work. 

Assuming  that  one-third  of  the  complete  day  is  spent  in 
work  and  two-thirds  in  rest,  the  figures  of  Atwater  and 
Benedict  give  2612  calories  as  the  quantity  of  heat  pro- 
duced by  the  average  working  man  in  24  hours. 

From  these  figures  it  is  easy  to  calculate  in  familiar  terms 
the  heating  effect  of  a  large  number  of  persons  in  a  subway 
or  other  confined  space.  Since  each  calorie  is  equivalent 
to  3.968  British  thermal  units,  2219  calories  are  equivalent 
to  8804  B.  T.  U.,  or  about  two-thirds  of  the  total  heating 
value  of  one  pound  of  good  coal.  If  allowance  is  made  for 
the  unavoidable  losses  which  occur  when  attempts  are 
made  to  heat  air  by  burning  coal,  it  appears  that  the  heat 
given  off  per  day  per  person  will  be  more  than  that  pro- 
duced by  the  use  of  one  pound  of  coal.  This  is  equivalent 
to  about  14  cubic  feet  of  illuminating  gas. 

Moisture  produced  by  human  beings.  The  amount  of 
moisture  given  off  by  the  breath  depends  somewhat  upon 
the  temperature  of  the  surrounding  air.  According  to 
Landois  and  Rosemann,2  the  least  production  of  moisture 
occurs  when  the  temperature  is  60  degrees  Fahrenheit. 
These  authorities  consider  that  the  total  quantity  given 
off  in  24  hours  ranges  from  330  to  640  grams.  This, 
in  familiar  terms,  is  equivalent  to  about  .7  of  a  pint  to  1 .3 
pints  of  water. 

1  Atwater  and  Benedict,  Bull.  109,  U.  S.  Dept.  Agri.,  p.  142,  1898- 
1900. 

'  Lehr.  Physiol.  des  Men.,  Berlin,  1905,  llth  Ed.,  p.  230. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      39 


Among  the  most  accurate  determinations  of  the  moisture 
produced  by  the  breath  are  those  of  Atwater  and  Benedict.1 
Their  figures  are,  for  periods  of  rest  and  work: 


Rest 

Work 

7a       lp 

Grams  per  hour 
18  41 

Grams  per  hour 
84  92 

IP       7P 

19  28 

87  29 

7P  _ia 

19  76 

26  62 

ja  —  la  . 

17.40 

20.64 

Average  D6r  hour          .               ... 

18.70 

54.87 

(14  experi- 
ments) 

(21  experi- 
ments) 

At  this  rate  every  one  hundred  people  at  rest  give  to  the 
air  nearly  half  a  gallon  of  water  per  hour. 

Amount  of  space  required  for  decency,  comfort  and 
safety.  Authorities  differ  as  to  the  amount  of  space 
required  by  human  beings  without  respect  to  the  quantity 
of  air  supplied  by  ventilation.  A  space  which  contains  a 
large  number  of  cubic  feet  per  person  provides  for  a  storage 
of  air  which  may  be  drawn  upon  in  emergency,  affords 
superior  opportunities  for  natural  air  currents  which  aid  in 
diffusing  impurities  and  gives  additional  chances  for  air  to 
enter  and  leave  through  openings  to  the  outer  air. 

Billings2  gives  as  the  smallest  amount  of  cubic  space 
permissible  for  common  lodgings  and  tenement  houses  300 
cubic  feet,  and  for  school  rooms  250  cubic  feet,  while  for 
hospitals  he  suggested  1000  to  1400  cubic  feet,  depending 
on  the  requirements  of  the  particular  cases  to  be  treated. 
Landois  and  Rosemann 3  give  for  dwelling  rooms  795  cubic 

1  Bull.  136,  U.  S.  Dept.  Agri.,  1900,  p.  147. 
3  Princ.  of  Ventilation,  N.  Y.,  1893,  p.  135. 
8  Lehr.  Physiol.  des  Men.  Berlin,  1905,  llth  Ed.,  p.  245. 


40          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

feet  and  for  rooms  occupied  by  the  sick  994  cubic  feet. 
For  school  children  in  England  the  requirement  is  80  cubic 
feet  with  a  floor  space  of  8  square  feet.  The  standard  for 
factories  in  England  is  250  cubic  feet  per  person. 

No  standard  has  ever  been  proposed  for  subways  or 
subway  cars.  When  the  cars  are  full  and  passengers  are 
sitting  and  standing  in  close  personal  contact  with  a  roof 
overhead  which  can  almost  be  touched  by  the  hand,  it  is 
needless  to  remark  that  neither  comfort  nor  decency  exist. 
The  consequences  which  would  follow  if  a  train  of  crowded 
cars  should  stop  and  the  ventilation  should  in  some  way  be 
entirely  shut  off  may  be  calculated.  In  the  cars  of  the  first 
New  York  subway  during  rush  hours,  each  passenger  had 
about  2  square  feet  to  stand  on  and  an  allowance  of  from 
15  to  25  cubic  feet  of  space.  We  may  assume  a  reserve 
space  of  about  2000  cubic  feet  of  air  distributed  between 
the  bodies  of  the  passengers  and  between  their  heads  and 
the  roof.  If  there  were  one  hundred  passengers  in  a  car, 
they  would  give  off  about  850  liters  of  air  loaded  with  4 
per  cent  of  carbon  dioxide  per  minute.  Within  six  minutes 
the  carbon  dioxide  in  the  air  of  the  car  would  reach  36 
parts  per  10,000,  the  air  would  smell  unpleasant,  every- 
thing would  be  damp  and  the  passengers  would  be  breath- 
ing rapidly.  It  is  practically  certain  that  some  would 
become  nauseated  and  that  nearly  all  would  be  panic 
stricken  and  likely  to  do  one  another  bodily  harm  before 
the  air  became  irrespirable.  But  if  they  remained  quiet, 
they  would  probably  not  be  suffocated  for  nearly  an 
hour. 

Fortunately  it  is  impossible  for  this  picture  to  be  realized 
so  far  as  ordinary  operating  conditions  are  concerned. 
No  cars  are  quite  tight  nor  could  they  be  made  so.  The 
amount  of  air  which  could  enter  and  leave  the  transoms, 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      41 

open  doors  and  windows  if  the  cars  were  stalled,  would  keep 
the  passengers,  even  in  subways  far  beneath  the  surface  of 
the  ground,  alive  indefinitely,  so  long  as  the  general  air  of 
the  subway  remained  good.  It  would  take  only  a  scarcely 
perceptible  air  current  passing  through  a  subway  to  keep 
the  air  pure  enough  to  avoid  the  suffocation  of  the  pas- 
sengers. 

Supply  of  air  required.  In  strictness,  the  amount  of  air 
to  be  supplied  per  hour  in  order  to  keep  the  carbon  dioxide 
of  an  enclosed  space  down  to  a  given  standard  depends 
ultimately  upon  the  number  of  persons  present  and  the 
number  and  nature  of  the  lights.  Enclosed  spaces  which 
are  continually  occupied  require  the  same  amount  of 
ventilation,  irrespective  of  their  size. 

The  standards  which  have  been  laid  down  as  to  the 
amount  of  carbon  dioxide  which  ought  not  to  be  exceeded 
in  the  air  of  enclosed  spaces  have  been  based  partly  upon 
the  unpleasant  sensations  produced  by  air  and  partly  upon 
considerations  of  expediency:  that  is,  what  it  has  been 
found  practicable  to  attain  in  the  way  of  ventilation. 

The  demand  for  better  conditions.  Through  the 
enlightening  effects  of  education,  higher  standards  of 
living  are  constantly  being  erected  and  these  are  bringing 
about  a  desire  for  more  decent  and  tolerable  conditions 
everywhere.  The  time  has  passed  when  sanitarians  found 
it  necessary  to  declare  a  condition  perilous  to  health  before 
demanding  that  it  be  improved.  If  air  is  decidedly  uncom- 
fortable by  reason  of  odor,  heat  or  dust,  abundant  warrant 
exists  for  bettering  it. 

In  a  similar  way  considerations  of  self  respect  are  urged 
as  reasons  for  demanding  that  adequate  space  be  provided 


42          THE  AIR  AND   VENTILATION   OF   SUBWAYS 

for  people  to  work  and  live  in.  Those  who  champion  this 
cause  argue  that  it  is  degrading  for  human  beings  to  be 
packed  as  close  as  it  is  physically  possible  for  them  to  be 
packed.  There  is  here  a  demand  that  provision  be  made 
for  what  may  be  termed  decency  as  distinguished  from 
health.  Practically  the  two  are  inseparable. 

How  far  the  requirements  of  public  comfort  will  extend 
in  the  future  to  underground  roads  it  is  impossible  to  say, 
but  it  seems  not  unlikely  that  the  public  will  insist  more  and 
more  upon  having  air  which  is  clean,  air  which  is  not 
uncomfortably  hot,  reasonable  freedom  from  unnecessary 
noise,  ample  artificial  light  where  natural  light  is  not 
procurable,  abundant  provision  against  accident  and 
sufficient  carrying  capacity  to  enable  passengers  to  travel 
with  expedition  and  decency. 

In  the  light  of  these  facts,  the  use  of  steam  locomotives 
in  unventilated  subways  and  long  tunnels  appears  bar- 
barous and  is  no  longer  to  be  thought  of.  It  has  been 
shown  that  effective  systems  for  renewing  the  air  are 
entirely  practicable  and  by  no  means  exorbitantly  expen- 
sive if  provided  for  when  the  road  is  designed.  In  the 
sanitary  provisions  of  these  tunnels  may  be  found  the 
secret  of  success  or  failure  in  subway  ventilation  as  in 
ventilation  everywhere.  Good  results  do  not  come  by 
accident.  Proper  ventilation  can  be  obtained  only  by 
deliberate  intention.  It  should  be  provided  for  in  advance. 
The  ventilation  should  be  arranged  for  when  the  structure 
is  designed. 

Standards  of  purity  for  the  air  of  subways.  There  is  room 
for  difference  of  opinion  concerning  proper  standards  of 
purity  for  subway  air,  the  standards  employed  in  the  past 
having  been  generally  those  which  hygienists  have  come  to 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR     43 

agree  upon  as  suitable  for  workshops,  schools  and  other 
public  buildings. 

It  may  be  asked  whether  these  standards  are  fair.  In 
some  cases  they  may  not  be  sufficiently  exacting,  for 
such  subways  as  the  Metropolitan  of  London  and  the 
Rapid  Transit  of  New  York  more  nearly  resemble  streets 
than  buildings.  Except  for  the  lack  of  sunlight,  the  gen- 
eral air  of  the  subway  may  actually  be  better  than  the 
air  of  the  streets.  On  the  other  hand,  deep  tubes  such 
as  those  of  London  are  far  below  the  streets  and  every 
consideration  makes  it  desirable  to  raise  a  high  standard 
for  them. 

Probably  a  reasonable  view  to  take  is  that  no  definite 
and  fixed  standards  should  be  erected  for  all  subways,  but 
the  air  of  each  should  be  kept  as  pure  as  necessary  to  meet 
the  sanitary  requirements  of  the  particular  place  in  ques- 
tion. In  other  words,  each  subway  should  be  considered 
on  its  own  merits. 

One  of  the  earliest  standards  was  that  of  Pettenkofer. 
Pettenkofer's  limit  was  10  volumes  of  carbon  dioxide  per 
10,000  volumes  of  air,  or,  as  he  supposed,  6  volumes  in 
excess  of  the  proportion  commonly  found  in  the  air  of 
cities  and  towns.  It  is  now  known  that  the  determinations 
of  carbon  dioxide  made  in  Pettenkofer's  time  were  about 
.5  parts  too  high. 

It  was  deChaumont  who  proposed  that  the  air  of  a  room 
should  be  maintained  at  such  a  state  of  purity  that  a  person 
coming  directly  from  the  external  air  should  perceive  no 
difference  in  odor  between  the  room  and  the  outside  air. 
In  order  to  accomplish  this  result,  he  proposed  that  the 
maximum  amount  of  carbon  dioxide  admissible  should  be 
two  volumes  in  excess  of  that  in  the  outside  air  after 
assuming  the  latter  to  average  about  4  parts  by  volume. 


44          THE   AIR   AND   VENTILATION   OF   SUBWAYS 

According  to  deChaumont's  dictum,  air  ceases  to  be  good 
when  the  carbon  dioxide  exceeds  8  volumes  and  is  exceed- 
ingly bad  when  10  or  more  volumes  are  present.1 

More  recently  a  standard  proposed  by  Carnelley,  Haldane 
and  Anderson,  for  crowded  schools,  was  13  volumes  of 
carbon  dioxide  per  10,000  volumes  of  air. 

As  a  result  of  their  work,  Haldane  and  Osborn2  recom- 
mended that  the  proportion  of  carbon  dioxide  in  the  air  at 
the  breathing  level  in  factories  and  away  from  the  imme- 
diate influence  of  special  sources  of  contamination,  such  as 
persons  or  lights,  should  not  rise  during  daylight,  or  after 
dark  when  only  electric  light  is  used,  beyond  12  volumes 
per  10,000  volumes  of  air  and  that  when  gas  or  oil  is  used 
for  lighting  to  not  over  20  volumes  after  dark. 

Calculation  of  fresh  air  requirements.  If  the  amount  of 
carbon  dioxide  produced  per  hour  expressed  in  fractions  of 
a  cubic  foot,  be  divided  by  the  amount  of  carbon  dioxide 
which  is  permissible,  also  expressed  in  this  way,  the  quo- 
tient will  be  the  number  of  cubic  feet  of  fresh  air  which  it 
is  necessary  to  introduce  in  order  to  dilute  the  carbon 
dioxide  to  the  proper  amount.  This  may  be  represented 
by  the  following  standard  formula: 


Here  Q  equals  the  number  of  cubic  feet  per  hour  of  fresh 
air  necessary,  C  the  volume  of  carbon  dioxide  in  cubic 
feet  produced  per  hour  by  one  person  and  P  the  amount 

1  DeChaumont,  Proc.  Roy.  Soc.  London,  Vol.  XXIII.,  p.  187. 
3  First  Report  of  the  Departmental  Committee  appointed  to  inquire 
into  the  ventilation  of  factories  and  workshops,  London,  1902,  p.  5. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR     45 

of  carbon  dioxide,  in  volumes  per  10,000  volumes  of  air, 
representing  the  permissible  standard  of  respiratory 
impurity.  It  is  evident  that  P  is  the  difference  between 
the  amount  of  carbon  dioxide  in  the  outside  air  and  in  the 
inside  air. 

Now  let  it  be  assumed  that  the  amount  of  carbon  dioxide 
given  off  by  the  average  adult  per  hour  is  0.6  cubic  foot 
and  that  the  permissible  impurity  is  represented  by  0.0002 
cubic  foot. 

Substituting  these  values  in  the  foregoing  formula,  we 

have, 

f\ 

=  300°  cubic  feet* 

This  is  the  number  of  cubic  feet  of  fresh  air  per  hour 
which  most  sanitarians  consider  is  necessary  per  person  for 
ventilation. 

The  amount  of  fresh  air  supplied  must  vary  with  cir- 
cumstances, however.  Billings  advises  from  1800  for 
office  rooms  to  3600  cubic  feet  of  fresh  air  per  hour  for 
hospitals. 

Effects  of  bad  ventilation.  The  injurious  effects  of  bad 
ventilation  are  often  considered  to  be  due  chiefly  to  want 
of  oxygen,  yet  other  factors  are  of  much  more  impor- 
tance. 

The  immediate  evils  are  generally  not  due  to  gases,  for 
unless  gas  lights  are  burning,  there  are  not  likely  to  be  any 
injurious  gases  present  in  sufficient  quantity  to  do  harm. 
Finally,  they  cannot  be  the  result  of  a  deficiency  of  oxygen, 
for  in  nearly  all  cases  there  is  sufficient  oxygen  present  in 
the  air  of  even  the  worst  ventilated  places  to  support  life 
easily.  In  many  places  which  appear  to  be  badly  venti- 


46          THE   AIR  AND    VENTILATION  OF   SUBWAYS 

lated,  but  in  which  the  air  has  been  proved  by  analysis  to 
be  sufficiently  pure,  headache  and  nausea  have  occurred. 

The  explanation  of  the  trouble  seems  to  lie  in  the  un- 
doubted effect  which  the  imagination,  properly  excited, 
may  have  upon  the  sensations.  A  tightly  closed  room, 
hot  and  ill-smelling,  is  quite  sufficient  to  produce  discom- 
fort. 

Tuberculosis  of  the  lungs  and  pneumonia  are  the  fatal 
diseases  most  prevalent  among  persons  living  and  working 
in  poorly  ventilated  rooms.  Both  of  these  diseases,  and  in 
fact,  practically  all  diseases  of  the  respiratory  tract,  are 
caused  by  bacteria  which  gain  access  to  the  air  passages. 
The  special  liability  of  persons  who  live  in  crowded  rooms 
is  probably  due  to  the  fact  that  the  rooms  become  infested. 
The  germs  also  are  transmitted  directly  from  person  to 
person. 

It  seems,  moreover,  not  improbable  that  an  impure 
atmosphere,  if  breathed  continually,  may  affect  the  vital 
and  bactericidal  powers  of  the  cells  and  fluids  of  the  upper 
air  passages  with  which  the  bacteria  come  in  contact  and 
may  thus  predispose  to  infection. 

For  persons  in  perfect  health,  most  bacteria  are  appar- 
ently harmless.  They  are  caught  for  the  most  part  by  the 
moist  linings  of  the  mouth,  nose  and  throat,  and  the  delicate 
cilia  of  the  respiratory  passages,  acting  like  countless 
scavengers,  probably  sweep  them  out  as  fast  as  they 
become  entangled  in  the  fluids  with  which  the  passages  are 
bathed. 

Most  of  the  bacteria  which  are  breathed  in  as  far  as  the 
trachea  and  bronchial  tubes  are  ultimately  swallowed  and 
pass  into  the  stomach.  So  long  as  the  passages  remain  in 
a  healthy  condition  the  danger  appears  to  be  compara- 
tively slight. 


CHARACTERISTICS  OF  GOOD  AIR  AND  BAD  AIR      47 

The  danger  is  greatly  increased  when  the  surfaces  become 
injured,  as,  for  example,  in  catarrh.  In  this  case  the 
mechanical  arrangements  for  ejection  are  put  out  of  service, 
the  secretions  are  only  imperfectly  expelled  and  bacteria 
are  sucked  down  into  the  air  cells.  Broncho-pneumonia 
and  other  obstructive  changes  are  natural  consequences. 

Poor  ventilation  frequently  leads  to  headache  and,  in 
some  cases,  nausea  after  an  exposure  of  only  a  brief  interval 
of  time  —  too  brief  an  interval  to  enable  us  to  conclude 
that  the  harm  is  due  to  bacteria,  and  we  must  seek  to 
account  for  it  on  other  grounds.  Continued  work  in  a 
closely  confined  atmosphere  reduces  vigor  in  an  unmis- 
takable manner.  It  finally  produces  a  cast  of  counte- 
nance which,  in  jails  and  penitentiaries,  is  termed  prison 
pallor. 

Inadequate  ventilation  in  mines  and  in  tunnel  construc- 
tion reduces  the  working  capacity  of  both  laborers  and 
foremen  to  an  extent  which  is  comparable  only  with  the 
effects  of  malarial  fever.  As  many  experienced  employers 
have  found,  much  more  work  is  done,  the  health  of  all  is 
preserved  and  many  indirect  economies  result  in  reduced 
cost  when  a  working-place  is  supplied  with  an  ample  volume 
of  fresh  air. 


CHAPTER  III 

METHODS  OF  VENTILATING  SUBWAYS 
FUNDAMENTAL  CONSIDERATIONS 

Differences  in  the  problems  of  ventilating  subways, 
tunnels  and  mines.  At  first  sight  it  would  appear  that  the 
ventilation  of  city  subways  must  be  a  part  of  a  general 
problem  which  includes  the  ventilation  of  tunnels  and 
mines,  but  this  is  not  the  fact.  The  ventilation  of  mines 
is  quite  a  different  subject  from  the  ventilation  of  sub- 
terranean roads  in  which  trains « are  operated.  Not  only 
are  the  impurities  to  be  dealt  with  different  but  the  move- 
ments of  trains  in  subways  and  tunnels  produce  strong 
currents  which  would  seriously  interfere  with  the  slow, 
regular  movements  of  air  which  are  desired  in  mine  ven- 
tilation. 

The  ventilation  of  tunnels  to  be  used  by  coal  burning 
locomotives  is  also  a  different  problem  from  that  of  ven- 
tilating city  subways  operated  by  electric  power.  The 
ventilation  of  steam  tunnels  is,  in  some  respects,  a  simpler 
problem. 

It  is  the  gases  due  to  the  combustion  of  fuel  which  cause 
the  air  to  be  vitiated  in  ordinary  railway  tunnels;  it  is  the 
problems  which  arise  from  the  assembling  of  large  numbers 
of  people  which  must  be  solved  in  managing  the  air  of 
electrically  operated  subways.  In  the  one  case  we  have  to 
deal  chiefly  with  poisonous  gases  —  in  the  other  chiefly 
with  living  agents  of  disease. 

48 


METHODS  OF  VENTILATING  SUBWAYS  49 

Necessity  for  skill  in  design  and  maintenance.  There 
should  be  little  difficulty  about  maintaining  good  sanitary 
conditions  in  any  subterranean  road  providing  the  problem 
is  handled  in  the  right  way,  that  is,  put  in  the  hands  of 
persons  who  are  skilled  in  sanitary  matters. 

It  is  too  common  to  leave  sanitary  questions  to  persons 
whose  training  and  experience  have  been  exclusively  in 
other  directions  and  whose  interests  do  not  lead  them  to 
make  a  special  study  of  these  particular  problems. 

If  the  same  grade  of  proficiency  which  is  required  of 
persons  in  charge  of  structural  and  electrical  matters  was 
demanded  of  those  who  are  employed  to  attend  to  sani- 
tary questions,  the  air  of  subways  and  public  buildings 
would  be  better.  In  most  cases  enough  work  is  done  and 
enough  money  spent  to  maintain  good  sanitary  conditions. 
The  fault  is  that  this  work  is  unskillfully  directed. 

The  correct  management  of  the  air  of  a  subway  requires 
a  careful  handling  of  many  technical  questions.  The 
success  of  the  work  depends  upon  the  thoroughness  with 
which  the  scientific  elements  of  the  problem  are  taken  into 
consideration.  In  fact  in  some  modern  tunnels,  a  highly 
skillful  management  of  the  air  has  been  necessary  to  make 
construction  and  maintenance  possible. 

The  difference  between  the  conditions  which  surrounded 
the  building  of  the  St.  Got  hard  tunnel,  where  800  of  the 
workmen  died  through  defective  hygienic  arrangements, 
and  the  Simplon,  where,  in  face  of  unprecedented  obstacles, 
such  a  thing  as  vitiated  air  was  unknown,  and  the  hospitals 
empty,  shows  well  what  can  be  done  when  a  serious  effort 
is  made  in  sanitation. 

Physical  principles  involved.  Air,  like  other  ponderable 
substances,  has  certain  physical  properties  which  should 


50  THE  AIR  AND   VENTILATION  OF  SUBWAYS 

be  kept  carefully  in  mind  in  even  the  most  superficial 
consideration  of  questions  of  ventilation. 

Air  has  weight  and  it  is  due  to  differences  in  the  weight, 
caused  chiefly  by  differences  in  temperature,  that  winds 
are  formed  and  currents  established  which  cause  the  atmos- 
phere to  circulate  over  the  earth's  surface,  through  city 
streets  and  even  into  houses  and  subways.  One  cubic 
foot  of  dry  air  weighs  536.29  grains,  or  0.07661  pound,  at  the 
level  of  the  sea  and  at  32  degrees  Fahrenheit. 

The  weight  of  a  given  volume  of  air  varies  as  its  tem- 
perature, for  it  is  the  temperature  which  fixes  its  density. 
Air  increases  by  ?1^  of  its  volume  for  every  rise  of  1  degree 
Fahrenheit.  Thus  if  the  air  of  an  enclosed  space  is  30 
degrees  warmer  than  the  outside  atmosphere,  every  pound 
of  the  latter  will  weigh  about  1  ounce  more  than  the  same 
volume  of  air  inside.  It  is  for  this  reason  that  when  cold  air 
enters  a  room  from  an  open  window  it  sinks  to  the  floor 
and  does  not  mix  freely  unless  it  is  deflected  or  agitated 
in  some  manner. 

When  air  is  heated  it  expands,  becomes  less  dense,  and, 
being  then  lighter  than  the  surrounding  air,  rises.  It  is  for 
this  reason  that  hot  air  balloons  go  up,  chimneys  produce 
draughts,  and  many  enclosed  spaces,  such  as  rooms  and 
halls,  are  sometimes  ventilated.  It  might  be  supposed 
that  this  principle  could  be  applied  to  ventilate  a  subway, 
but  although  some  exchange  of  air  undoubtedly  takes 
place  in  all  subways  on  this  account,  it  cannot  usefully  be 
employed  to  move  all  the  air  necessary. 

Mechanical  principles.  The  flow  of  air  through  large, 
underground  passages  depends  not  only  upon  its  weight, 
but  upon  the  frictional  resistance  offered  by  the  walls  of 
the  passages.  To  force  air  through  an  airway  by  means  of 


METHODS  OF  VENTILATING  SUBWAYS  51 

fans  or  otherwise  often  requires  the  overcoming  of  much 
frictional  resistance. 

The  frictional  resistance  is  proportional  to  the  speed,  to 
the  perimeter  and  length  of  the  airway  and  an  arbitrary 
factor  which  depends  upon  the  form  and  roughness  of  the 
walls.  The  value  of  this  constant,  termed  K,  varies 
greatly,  so  that  it  is  unsafe  to  assume  any  value  for  it 
without  a  close  knowledge  of  the  conditions  to  which  it  is 
to  be  applied.  In  mine  ventilation  K  has  been  assumed 
to  vary  between  0.00000000158  for  a  straight,  brick-lined 
section,  to  0.00000001257  for  a  rough  and  crooked  one. 

Books  have  been  written  upon  the  calculations  necessary 
to  determine  the  best  forms  and  materials  with  which  to 
construct  ventilating  apparatus.  It  is  unnecessary  to 
enter  into  these  details  here,  but  a  fewr  of  the  familiar 
formulae  will  show  the  way  in  which  some  of  the  more 
useful  calculations  are  made. 

The  following  formulae  are  for  calculating  the  proper 
areas  of  passages,  velocity  of  air,  length  of  airways,  quan- 
tities of  air  delivered,  horse  power  and  pressure,  etc.; 

Let   A  =  area  of  passage  in  square  feet, 

H  =  horse  power  required  for  ventilation, 

K  =  coefficient  of  friction  due  to  the  movement  of 

air  through  the  airway, 
L  =  length  of  airway, 
0  =  circumference  of  airway, 
P  =  loss  in  pressure  in  pounds  per  square  foot, 
Q  =  cubic  feet  of  air, 

S  =  square  feet  of  surface  producing  friction, 
U  =  units  of  work  in  foot  pounds  to  move  the  air, 
V  =  velocity  of  air  in  lineal  feet  per  second, 
W  =  water  gage  in  inches. 


52  THE  AIR  AND  VENTILATION  OF  SUBWAYS 

For  the  area  of  the  cross  section  of  the  duct  necessary*  to 
accommodate  a  given  flow  of  air: 

A       KSV2       KSV2Q  =  KSV3        U     _  Q 
P  U  PV     =  PV    =  V' 

For  the  horse  power  required  to  deliver  the  air: 
U  QP        5.2  QW 


2'     H  '~    33,000        33,000       33,000  " 

To  determine  the  frictional  resistance  offered  by  the  walls 
of  the  duct  to  the  flow  of  air: 

K=PA_       JL  P  5.2  TF 

SV2  ==  SV3  '     SV2  +  A  ~  SV2  -J-  A  ' 

For  the  pressure  in  pounds  per  square  foot : 
4.     P  •• 


3/U  \2KS  _KSV3  _    U 
)    A  Q      *  AV 


For  the  quantity  of  air  moved  in  cubic  feet  per  minute  : 


To  determine  the  units  of  work  in  foot  pounds  to  deliver 
the  air  : 


6.     U  =  QP  =  VPA  =  =  KSV 

j\. 

=  5.2  QW  =  33,000  H. 


METHODS  OF  VENTILATING  SUBWAYS  53 

To' ascertain  the  velocity  of  the  air  in  a  duct: 

u      Q 
7-       S~PA"~~A 

To  determine  the  water  gage: 
P       KSV2 


8.     W  = 


5.2       5.2  A 


Physical  principles  involved  in  subway  heating  and  cool- 
ing. The  heating  of  subways  affects  the  comfort  of  the 
travelling  public  to  such  an  extent  that  it  may  be  well 
briefly  to  refer  here  to  some  of  the  physical  principles 
which  must  be  taken  into  account  in  disposing  of  the  heat. 

The  warm  air  of  a  subway  is  due  to  the  heat  produced 
by  the  machinery  and  brakes  on  the  trains.  The  heat 
generated  from  the  bodies  of  passengers  is  inconsiderable 
when  compared  with  the  amount  which  is  due  to  the 
consumption  of  energy  used  in  operating  the  trains.  Were 
it  not  for  the  mechanical  losses  due  to  the  production  and 
transmission  of  the  electric  current,  the  heat  produced  in  a 
subway  would  be  the  same  as  though  the  coal  used  up  at 
the  power  house  was  consumed  in  fires  along  the  track. 

The  only  way  for  the  heat  to  disappear  is  to  escape 
through  the  walls  or  by  the  air. 

When  hot  motors  and  brake  shoes  pass  through  a  subway 
they  lose  their  heat  by  radiation  and  conduction,  the  large 
volumes  of  air  which  flow  over  them  greatly  favoring  the 
removal  of  heat  in  the  latter  manner.  The  heating  of  rooms 
by  stoves  and  steam  pipes  occurs  largely  in  the  same  way; 
in  this  case,  however,  the  air  is  brought  into  contact  with 
the  hot  surfaces  chiefly  through  currents  set  up  by  the 


54          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

heat  itself.  The  action  of  these  currents  constitutes  a 
special  form  of  conduction  called  convection. 

The  walls  of  a  subway  become  heated  through  the  direct 
effect  of  radiation  from  the  trains  and  by  absorbing  heat 
from  the  air  and  they  transmit  the  heat  to  the  cooler  earth 
beyond  them.  The  rate  of  transmission,  called  thermal 
conductivity,  differs  with  different  substances.  The  rate 
varies,  also,  with  the  thickness  of  the  body  through  which 
the  heat  is  transmitted  and  the  difference  of  temperature 
at  the  two  sides. 

When  subways  are  first  put  in  operation  much  of  the 
heat  produced  by  the  cars  is  transmitted  through  the  metal 
and  masonry  linings  to  the  earth  surrounding  them,  but  in 
course  of  time  this  earth  becomes  warm  also,  and  little  more 
heat  can  be  absorbed.  The  subway  air  then  grows  warmer 
and  unless  some  special  means  of  removing  the  heat  is 
provided,  the  air  may  become  very  uncomfortable.  The 
most  practicable  means  of  cooling  a  subway  is  to  provide 
for  a  very  large  amount  of  ventilation. 

PRACTICAL  SYSTEMS  IN  USE 

The  ways  in  which  subways  have  been  ventilated  may 
conveniently  be  considered  under  four  separate  heads : 

1.  By  introducing  or  exhausting  air  at  various  points  by 
means  of  fans. 

2.  By  forcing  a  current  of  air  from  one  end  to  the  other 
of  the  whole  line  by  fans. 

3.  By  so-called  natural  ventilation. 

4.  By  the  piston  action  of  trains. 

The  exhaust  and  plenum  principles.  Fans  are  almost* 
invariably  employed  to  exhaust  air,  not  to  supply  it.  They 


METHODS  OF  VENTILATING  SUBWAYS  55 

may  exhaust  through  side  chambers  directly  to  the  outside 
air,  as  in  the  older  portions  of  the  Boston  subway,  or  by 
means  of  air  ducts  communicating  at  various  points,  as  in 
the  Severn  and  Mersey  tunnels.  In  the  former  case  a 
number  of  comparatively  small  ventilating  fans  are  em- 
ployed at  the  points  where  the  air  is  to  be  extracted ;  in 
the  latter,  large  central  pumping  plants  are  used.  In  any 
case  fresh  air  is  expected  to  enter  at  stations  or  other 
appropriate  points  as  rapidly  as  the  foul  air  is  exhausted. 

In  the  plenum  principle  the  fresh  air  is  forced  in  by  the 
fans  and  the  foul  air  escapes  as  best  it  can.  This  method 
is  more  often  used  to  supply  air  during  construction  of  deep 
subways  than  in  subways  after  they  are  built. 

Many  arguments  have  been  brought  forward  to  show  the 
advantage  of  renewing  the  air  at  stations  rather  than 
elsewhere. 

It  has  been  urged,  for  example,  that  the  air  should  be 
exhausted  between  stations  and  allowed  to  flow  in  at  the 
stations  since  (a)  more  passengers  are  congregated  at 
stations  than  at  other  points  and  in  this  way  they  will  get 
the  freshest  air;  (6)  the  air  in  the  cars  is  renewed  at  sta- 
tions not  between  them,  so  the  air  should  be  at  its  best 
there;  (c)  this  method  would  most  rapidly  remove  smoke 
and  heat  in  case  of  fire  and  give  the  best  opportunity  for 
escape  through  the  stations. 

Some  of  these  arguments  are  valid  while  others  involve 
refinements  of  logic  which  seem  scarcely  justified.  If  the 
air  is  renewed  as  frequently  as  it  should  be,  it  makes  little 
difference  from  a  sanitary  standpoint  at  what  places  it  is 
introduced  or  exhausted. 

1.  Action  of  fans  applied  at  various  points.  The  earliest 
use  of  a  fan  for  assisting  the  ventilation  of  a  railway  tunnel 


56          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

is  believed  to  have  been  in  1870  in  connection  with  the  Lime 
Street  tunnel  of  the  London  and  Northwestern  Railroad 
at  Liverpool. 

Following  the  generous  proportions  of  fans  which  had 
been  employed  in  ventilating  mines,  this  fan  was  29J  feet 
in  diameter  and  discharged  its  air  into  a  conical  brick 
chimney  54  feet  in  diameter  at  the  base.  The  quantity  of 
air  thrown  was  431,000  cubic  feet  per  minute.  The  air 
was  taken  from  a  point  midway  between  the  two  ends  of 
the  tunnel.  The  tunnel  was  6075  feet  in  length.1 

Fans  in  the  Boston  subway.  The  Boston  subway  is  about 
4J  miles  long  and  is  operated  by  electricity.  It  is  used  by 
trains  and  single  trolley  cars,  most  of  whose  routes  lie  in 
the  open  air.  The  speed  is  so  slow  that  the  ventilating 
currents  set  up  by  the  moving  cars  are  often  scarcely 
noticeable.  The  typical  section  is  332  square  feet  where 
the  subway  is  occupied  by  two  tracks  and  707  square  feet 
where  it  is  four  tracks  wide. 

In  the  section  of  the  road  first  built  ventilating  fans  are 
placed  in  chambers  alongside  of  the  subway  at  points 
between  stations  and  the  air  is  discharged  upward  through 
grated  openings  in  the  sidewalks  overhead  or  through 
short  shafts  to  the  outer  air.  The  fans  are  7  to  8  feet  in 
diameter.  They  were  intended  to  be  of  such  capacity  as 
to  enable  them  to  completely  renew  the  air  every  ten 
minutes.  Fig.  3. 

In  the  section  under  the  harbor  the  same  general  plan 
is  followed  of  taking  air  in  at  the  stations  and  removing  it 
between  stations.  In  this  case,  however,  an  exhaust  duct 
has  been  placed  along  the  top  of  the  tunnel  with  occasional 
openings  which  can  be  opened  or  closed  at  pleasure.  The 
cross  section  of  the  duct  is  about  48  square  feet;  the  open- 
1  Francis  Fox,  Trans.  Am.  Soc.  C.  E.,  Vol.  54,  Part  C,  p.  554. 


METHODS  OF  VENTILATING  SUBWAYS 


57 


ings  are  about  4  feet  long  and  1  foot  5  inches  wide  and 
they  are  placed  at  intervals  of  about  550  feet. 

The  air  is  withdrawn  at  each  end  of  the  tunnel  and 
exhausted  by  means  of  fans  through  shafts  about  one  mile 
apart,  on  the  opposite  shores.  At  the  East  Boston  end 


TREMONT  ST 

Surface  of 
St 


FIG.  3.     Method  of  Ventilating  the  Boston  Subway  with  Fans. 

the  air  is  exhausted  through  grated  openings  in  the  side- 
walk 40  feet  long  and  7  feet  1  inch  wide.  At  the  other 
end  the  air  is  discharged  about  21  feet  above  the  surface  of 
the  street. 

The  fans  consist  of  two  8  foot  vertical  fans  at  the  East 
Boston  end  and  two  7  foot  horizontal  fans  at  the  Atlantic 


58          THE  AIR  AND  VENTILATION  OF  SUEWAYS 

Avenue  shaft.  At  175  to  218  revolutions  per  minute  and 
about  12  horse  power  each,  the  total  rated  capacity  of  the 
whole  ventilating  plant  is  90,000  cubic  feet  per  minute. 
This  gives  a  theoretical  velocity  for  the  whole  air  in  the 
tunnel  of  about  2J  feet  per  second  and  is  equivalent  to  a 
renewal  of  the  air  every  15  minutes. 

A  complete  description  of  the  ventilation  arrangements 
of  the  Boston  subway  has  been  given  by  Mr.  H.  A.  Carson, 
M.  Am.  Soc.  C.  E.,  Chief  Engineer  of  the  Boston  Transit 
Commission  in  the  Proceedings  of  the  American  Society  of 
Mechanical  Engineers,  Vol.  28,  pp.  927~942. 

Fans  in  the  Severn  and  Mersey  tunnels.  The  Severn 
tunnel,  of  the  Great  Western  Railway,  was  opened  in  1886. 
It  is  about  4f  miles  long.  It  is  occupied  by  two  tracks  for 
steam  railway  travel.  There  is  a  ventilating  shaft  located 
near  the  center  through  which  air  is  exhausted  by  means 
of  a  fan  40  feet  in  diameter.  It  is  said  that  the  capacity 
of  the  fan  is  sufficient  to  renew  the  air  of  the  tunnel  about 
every  ten  minutes.  (See  Fig.  4.) 

The  Mersey  tunnel,  connecting  the  cities  of  Liverpool 
and  Birkenhead,  is  about  2  miles  long  and  is  occupied  by  a 
double  line  of  electric  railway.  Air  is  exhausted  through 
numerous  passages  communicating  with  ventilating  gal- 
leries which  lead  to  exhaust  fans.  These  fans  are  from  12 
to  40  feet  in  diameter  and  are  located  at  stations  above 
ground.  The  combined  capacity  of  these  fans  is  estimated 
to  be  about  950,000  cubic  feet  per  minute  or  sufficient  to 
renew  the  air  of  the  tunnel  every  nine  minutes.  This 
tunnel  is  often  referred  to  as  affording  an  example  of  the 
most  perfect  system  of  artificial  ventilation  yet  devised. 
It  was  certainly  the  earliest  tunnel  in  which  a  comprehensive 
system  was  adopted.  (See  Fig.  5.) 


60 


THE  AIR  AND  VENTILATION  OF  SUBWAYS 


Fans  in  the  newest  London  tubes.  The  general  plan  of 
ventilating  the  new  tubes  of  the  Electric  Underground 
Railways  Company  is  to  take  advantage  of  the  piston 


action  of  the  trains,  as  do  all  the  London  subways,  and  to 
supplement  this  by  fans  at  the  stations. 
The  fans  exhaust  air  from  beneath  the  station  platforms 


METHODS   OF   VENTILATING    SUBWAYS  61 

and  carry  it  through  airways  averaging  12  to  16  feet  in 
cross  section  to  the  roofs  of  the  buildings  used  for  subway 
stations,  there  to  be  discharged  into  the  free  atmosphere. 
The  fresh  air  enters  through  these  station  stairways  and 
lifts.  (See  Fig.  6.) 

The  fans  are  of  a  designed  capacity  sufficient  to  remove 
1,000,000  cubic  feet  of  air  per  hour  when  working  at 
moderate  speed.  This  is  sufficient  to  renew  all  the  air  in 
the  average  length  of  subway  between  two  stations  in  each 
of  the  parallel  tunnels  every  thirty  minutes.  The  fans  are 
located  at  the  tops  of  the  buildings.  They  have  been 
found,  upon  test,  to  deliver  18,250  cubic  feet  per  minute 
when  operated  at  a  velocity  of  242  revolutions  per  minute. 
Great  care  was  used  to  avoid  vibration  and  noise  from  the 
motors  and  fans. 

2.  Action  of  fans  applied  at  one  end  of  a  subway.  — 

System  used  by  Central  London  Underground.  A  system 
of  forcing  air  through  an  electric  subway  has  been  in- 
stalled in  connection  with  the  Central  London  Under- 
ground, a  good  example  of  the  deep  London  tubes. 

The  ventilating  arrangement  of  the  Central  London 
Railway  is  capable  of  renewing  all  the  air  contained  in  this 
subway  three  times  over  every  night.  In  order  to  accom- 
plish this  result  double  doors  are  arranged  at  the  station 
entrances  and  shut  at  night.  The  air  flows  in  at  the  city 
end  of  the  Bank  of  England,  passes  through  the  two  tubes, 
each  over  six  miles  long,  and  is  exhausted  by  a  fan  at 
Shepherd's  Bush. 

The  fan  is  20  feet  in  diameter,  of  the  Guibal  type.  It 
is  said  to  be  capable  of  exhausting  100,000  cubic  feet  of 
air  a  minute  as  measured  at  a  point  near  the  far  end  of  the 
line.  During  the  day  it  is  not  possible  to  run  this  fan  with 


62          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

much  effect,  because,  with  the  opening  of  the  station  doors 
by  passengers,  it  draws  air  from  the  stations,  chiefly  from 
the  nearest  one.  But  at  night  after  the  last  train  has  been 
run  out  of  the  subway  on  the  surface  at  the  west  end  all 
the  doors  are  closed  and  the  fan  is  started.  It  is  kept 
going  until  the  first  train  is  run  in  the  morning.  The 
results  are  said  to  be  excellent. 

3.  Natural  ventilation.  Although  many  subways  are 
now  provided  with  some  system  of  ventilation  requiring 
the  use  of  fans,  by  far  the  greatest  number  still  depend  for 
a  circulation  of  air  upon  currents  set  up  without  special 
mechanical  aid. 

Blow-holes.  Among  the  more  common  ways  of  securing 
this  so-called  natural  ventilation,  the  use  of  blow-holes,  or 
free  openings  to  the  outside  air,  deserve  special  notice.  It 
is  to  ventilation  accomplished  in  this  way  that  the  frequent 
renewal  of  air  in  the  New  York  subway  is  due. 

The  draught  of  air  passing  through  the  blow-holes  is 
sometimes  violent.  An  average  velocity  of  16J  miles  per 
hour  through  the  stairways  of  the  New  York  subway  was 
observed  in  the  author's  investigations  as  a  result  of 
several  hours'  observation  with  anemometers.  Had  this 
current  taken  place  through  one-half  of  the  openings 
between  96th  Street  and  the  Brooklyn  Bridge  the  quantity 
of  air  so  supplied  would  have  been  capable  of  renewing  the 
entire  atmosphere  of  the  subway  every  few  minutes. 

At  first  sight  it  would  appear  that  nothing  could  be 
easier  than  to  ventilate  a  subway  by  this  means.  It  seems 
as  simple  as  opening  the  window  of  a  living  room.  Yet  to 
get  the  best  effects  from  blow-holes,  ventilation  means 
much  more  than  the  mere  opening  of  the  roof.  To  provide 
for  a  suitable  and  reliable  movement  of  air  requires  careful 


METHODS   OF   VENTILATING   SUBWAYS  63 

study.  Apparently  the  very  simplicity  of  the  idea  of 
blow-hole  ventilation  has  prevented  the  development  of 
this  principle  in  the  best  manner.  To  some  subways  and 
tunnels  it  is  peculiarly  suited. 

The  term  blow-hole  is  here  used  to  include  all  openings 
through  which  the  confined  air  can  escape  and  fresh  air 
enter,  whether  they  be  stairways,  openings  in  the  roof  or 
openings  through  side  chambers.  In  shallow  subways 
such  openings  usually  pierce  the  roof  or  lead  from  station 
platforms  with  more  or  less  directness  to  the  outside  air. 
They  are  usually  much  too  small,  too  indirect  and  too  long 
to  accomplish  all  the  benefit  which  may  be  obtained  from 
them. 

Inasmuch  as  the  flow  of  the  air  is  impeded  by  friction 
against  the  walls,  blow-holes  should  be  as  short  as  prac- 
ticable. Since  the  friction  increases  as  the  square  of  the 
velocity  of  the  current  and  inversely  as  the  diameter  of 
the  passage,  they  should  be  large  in  section  and  but  little 
obstructed  by  screens,  doorways,  nettings  and  other 
incumbrances. 

It  is  easy  to  see  that  blow-holes  may  be  more  advanta- 
geously employed  in  subways  built  near  the  surface  of  the 
ground  than  in  railways  far  beneath  the  surface.  And  yet 
this  is  the  only  way  in  which  some  of  the  deep  London 
tubes  are  ventilated. 

Direction  of  openings  with  respect  to  wind.  If,  as  some- 
times happens,  the  blow-holes  are  open  stairways  covered 
by  cowl-like  kiosks,  the  direction  of  the  openings  with 
respect  to  prevailing  breezes  may  materially  aid  or  interfere 
with  the  amount  of  air  which  passes  in  or  out.  Let  us 
briefly  examine  this  effect. 

A  breeze  which  is  just  perceptible  may  be  assumed  to 
travel  at  a  velocity  of  2.92  feet  per  second  and  to  exert  a 


64          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

pressure  of  0.02  pounds  per  square  foot  and  a  breeze  of 
twice  this  velocity  exercises  four  times  this  pressure.  A 
brisk  wind  travelling  at  a  velocity  of  25  miles  per  hour  or 
36  feet  per  second,  a  not  uncommon  occurrence  in  New 
York  at  some  seasons  of  year,  exercises  a  pressure  of  about 
3  pounds  per  square  foot.  A  wind  of  45  miles  exercises 
a  pressure  of  10  pounds.  If  a  pleasant  breeze  of  2J  miles 
per  hour  acts  full  upon  a  kiosk  such  as  many  of  those  which 
stand  over  the  New  York  subway,  measuring  5}  X  1\ 
feet,  it  is  as  effective  as  two  fans,  each  6  feet  in  diameter, 
turning  at  the  rate  of  200  revolutions  per  minute  and 
delivering  21,200  cubic  feet  of  air  per  minute. 

4.  The  piston  action  of  trains.  The  action  of  moving 
trains  is  more  important  than  any  other  factor  in  estab- 
lishing a  circulation  of  air  through  blow-holes.  This  so- 
called  "  piston,"  or  "  plunger "  action  has  long  been 
recognized  as  useful,  but  it  has  remained  for  the  New 
York  subway  to  demonstrate  how  extremely  beneficial  it 
may  be. 

The  main  principle  of  the  phenomenon  of  piston  action 
is  easily  understood.  The  moving  trains  force  air  ahead 
of  them  and  cause  air  to  rush  in  after  they  are  passed. 

The  action  is  probably  to  be  regarded  as  a  combination 
of  the  principle  of  a  fan  in  which  there  is  practically  no 
displacement  and  the  principle  of  a  plunger  in  which  the 
displacement  produces  the  whole  effect.  The  plunger 
action  is  greatest  at  stations  and  other  enlargements  of  the 
subway  and  where  the  speed  is  slow.  The  fan  action  is 
most  important  where  the  speed  is  high  and  where  the 
train  fits  the  subway  most  completely. 

The  quantity  of  air  moved  depends  upon  many  circum- 
stances. Chief  of  these  are  (a)  the  extent  to  which  the 


METHODS  OF  VENTILATING  SUBWAYS  65 

tunnel  section  is  filled  by  the  section  of  the  train;  (b)  the 
speed  of  the  train;  (c)  the  opportunity  afforded  by  blow- 
holes for  the  air  to  flow  in  and  out;  and  (d)  the  shape  of 
the  forward  end  of  the  train.  These  facts  seem  too  obvious 
to  need  discussion. 

Berlin-Zossen  tests.  In  studies  made  on  the  Berlin- 
Zossen  Railway  into  the  resistance  offered  by  the  free 
outside  atmosphere  to  the  movement  of  trains,  it  was 
found  that  air  piled  up  in  front  of  the  first  car  in  the  form 
of  a  cone  of  increased  pressure  and  that  a  cone  of  reduced 
pressure  followed  behind  the  train.  For  example,  the 
pressure  in  front  of  a  car  (which  presented  a  face  perpen- 
dicular to  the  line  of  the  track)  was  4.09  pounds  per  square 
foot  at  a  speed  of  12.4  miles  per  hour;  6.14  pounds  at  18.6 
miles;  8.19  pounds  at  24.8  miles.  This  pressure  was  main- 
tained for  between  10  and  16  feet  in  front  of  the  moving 
train;  beyond  this  it  gradually  fell  off.1 

Official  observations  in  Paris  subway.  A  Commission 
appointed  by  the  Prefect  of  the  Seine  to  study  the  ven- 
tilation of  the  Metropolitan  Subway  of  Paris  gave  some 
attention  to  the  air  currents  which  circulated  about  the 
trains.  The  air  flowed  ahead  of  the  train  until  the  front 
of  the  train  was  immediately  opposite  the  observer,  when 
there  was  a  sudden  gust  and  the  flow  changed  to  a  direc- 
tion opposite  that  of  the  train  movement.  After  the  train 
passed,  air  followed  it  for  about  one  minute.  When  the 
train  moved  at  the  rate  of  about  3  feet  per  second,  less 
than  2  miles  per  hour,  air  165  feet  ahead  of  the  train  moved 
at  about  the  same  velocity. 

Observations  in  New  York  subway.  Observations  made 
by  the  author  have  shown  that  in  the  New  York  subway 
before  any  material  changes  were  made  in  the  arrange- 

1  Street  Railway  Journal,  New  York,  October  28,  1905,  p.  802. 


66 


THE  AIR  AND   VENTILATION  OF  SUBWAYS 


ments  for  ventilation,  with  the  ordinary  train  service  of 
early  afternoon,  air  passed  from  one  station  to  another 
sometimes  at  a  rate  of  over  8  miles  per  hour  and  at  an 


FIG.  7.  Air  Currents  Set  up  by  an  Express  Train  Passing  through  the 
Simplest  Form  of  Station  in  the  New  York  Subway. 

average  rate  of  about  3  miles.  The  approach  of  a  train 
toward  a  station  on  the  four-track  road  could  be  felt  by 
the  flow  of  air  ahead  of  it  while  the  train  was  over  1000 
feet  away.  (See  Figs.  7,  8,  9  and  10.) 


METHODS  OF  VENTILATING  SUBWAYS 


67 


In  observations  made  for  the 
author  in  the  Berlin  subway, 
the  movement  of  air  was  always 
easily  detected  while  the  train  was 
800  feet  off  and  continued  in  the 
opposite  direction  for  at  least  25 
seconds  after  the  train  had  passed. 
In  the  New  York  subway  even 
when  no  trains  could  be  heard  in 
either  direction  a  distinct  but  faint 
current  moved  on  each  side  of  the 
road  in  the  direction  of  the  general 
train  movement. 

The  express  trains  produced  the 
greatest  amount  of  ventilation  in 
the  New  York  subway,  although 
the  action  of  both  express  and 
local  trains  was  of  value.  The  ex- 
presses were  of  special  service  in 
that  they  passed  through  the  local 
stations  at  full  speed  and  by  their 
high  velocity  caused  especially  ener- 
getic currents  of  air  to  pass  in  and 
out  of  the  stairways  and  openings 
in  the  roof.  A  somewhat  detailed 
study  was  made  of  the  direction  of 
currents  set  up  by  express  trains 
at  several  stations. 

Peculiar  value   of  piston   action. 
The  exhaling  and   inhaling   action 
due  to  the  operation  of  trains  is  of 
peculiar  value  in  that  it  occurs  when  and  where  most  needed, 
provided,  of  course,  that  the  openings  to  the  outside  air 


68          THE   AIR  AND   VENTILATION   OF   SUBWAYS 


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METHODS  OF  VENTILATING  SUBWAYS 


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THE  AIR  AND   VENTILATION  OF  SUBWAYS 


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METHODS  OF  VENTILATING  SUBWAYS  71 

are  properly  placed  and  unencumbered.  The  greater  the 
number  of  passengers  carried  and  the  greater  the  number 
of  trains,  the  greater  is  the  amount  of  ventilation.  And 
not  the  least  conspicuous  of  the  advantages  of  so-called 
natural  ventilation  is  its  economy. 

No  expense  is  necessary  for  the  operation  of  mechanical 
devices  in  natural  ventilation.  Experience  with  the  New 
York  subway  shows  that  it  is  not  always  necessary  or 
desirable  for  a  train  to  fit  very  closely  into  the  tunnel 
section.  In  fact  it  is  conceivable  that  when  this  fit  is  close, 
the  cars  carry  along  more  of  their  own  air  than  desirable 
and  the  passengers  within  them  enjoy  much  less  interchange 
than  would  take  place  otherwise. 


CHAPTER  IV 

THE  AIR  OF  EUROPEAN  SUBWAYS 
METROPOLITAN  AND  DISTRICT  OF  LONDON 

ONE  of  the  first,  and,  in  some  respects,  most  interesting 
investigations  yet  made  concerning  the  ventilation  of  a  city 
subway  was  undertaken  in  1897  by  a  Committee  appointed 
by  the  London  Board  of  Trade.  The  main  object  of  the 
Committee  was  to  study  the  system  of  ventilation  of 
tunnels  on  the  Metropolitan  Railway  of  London  and  report 
whether  any,  and  if  so,  what,  steps  could  be  taken  to  add 
to  the  efficiency  of  the  ventilation  in  the  interest  of  the 
public. 

Work  of  an  official  investigating  committee.  The  Com- 
mittee consisted  of  Major  F.  A.  Marindin,  Earl  Russell, 
Sir  Douglas  Galton,  Sir  Charles  Scotter  and  Dr.  John  Scott 
Haldane.  In  the  course  of  the  Committee's  work,  thirty- 
six  witnesses,  including  eminent  scientists  and  engineers, 
as  well  as  employees  of  the  road,  were  called  upon  to 
testify  either  in  the  interest  of  the  public  or  of  the  three 
companies  which  operated  the  road. 

Among  the  companies'  representatives  were  Dr.  Henry 
Edward  Armstrong,  F.R.S.,  Sir  John  Wolfe  Barry,  Mr. 
Beauchamp  Tower  and  Sir  Benjamin  Baker.  Among  other 
expert  witnesses  were  Messrs.  Francis  Fox,  Harrison 
Hayter,  J.  C.  Inglis,  William  G.  Walker  and  Alexander  R. 
Binnie. 

72 


THE  AIR  OF  EUROPEAN  SUBWAYS  73 

The  Committee  held  formal  meetings  to  take  testimony 
and  made  personal  inspections  of  the  Metropolitan  and 
other  tunnels,  examining  air  currents  and  taking  samples 
of  air  for  analysis.  The  final  report  of  the  Committee, 
containing  the  minutes  of  the  meetings,  testimony  of 
witnesses  and  other  addenda,  is  the  source  from  which  most 
of  the  facts  concerning  the  investigation  have  been  taken. 

Operating  conditions.  During  the  busiest  times  of  the 
day  there  were  nineteen  trains  running  each  way  per  hour. 
In  nineteen  hours,  528  passenger  trains  and  fourteen 
freight  trains  passed  within  the  part  of  the  line  which 
received  the  greatest  amount  of  the  Committee's  attention. 
These  trains  were  capable  of  carrying  225,279  passengers. 
Each  locomotive  consumed  3  hundredweights  of  coal  and 
evaporated  330  gallons  of  water  per  hour.  The  coal  used 
was  called  " Welsh  smokeless"  coal.  The  engines  were  so 
constructed  as  to  limit  by  condensation  the  escape  of  steam 
whilst  the  engine  was  in  the  tunnel. 

The  part  of  the  railway  which  received  most  attention 
was  between  Edgware  Road  and  King's  Cross.  The 
distance  was  about  two  miles.  It  was  continuously  in 
tunnel  except  at  the  stations.  The  tunnel  was  16  feet  high 
from  the  rail  level  to  the  crown  of  the  arch  and  28  feet 
6  inches  at  its  widest  part. 

The  subway  was  ventilated  chiefly  by  blow-holes,  of 
which  there  were,  in  the  section  particularly  studied, 
thirteen. 

The  management  of  the  road  admitted  that  the  con- 
dition of  air  had  been  very  unsatisfactory  from  the  first. 
The  original  intention  had  been  to  operate  the  road  by  hot 
water  locomotives  and  for  this  reason  no  structural  pro- 
vision had  been  made  for  ventilation  except  such  as  might 


74          THE  AIR  AND   VENTILATION  OF  SUBWAYS 

occur  at  the  staircases.  The  hot  water  locomotives  proved 
a  failure  and  ordinary  locomotives  with  condensing  tanks, 
but  with  ordinary  coal,  were  at  first  employed.  The  air 
at  once  became  insufferable  and  permission  was  obtained 
to  tear  up  large  areas  of  one-inch  thick  glass  vault  lights 
on  Baker  Street,  Portland  Road  and  Gower  Street,  and 
substitute  gratings. 

Company's  experiments  with  ventilation.  This  was  the 
beginning  of  a  train  of  unsuccessful  experiments  which 
covered  about  35  years.  These  experiments  included 
blowing  air  at  the  rate  of  60,000  cubic  feet  per  minute  into 
the  subway  through  a  canvas  tube  under  the  station  plat- 
form at  Portland  Road,  the  idea  being  that  the  air  would 
distribute  itself  under  the  platform  and  come  up  under  the 
front  edge  so  that  people  standing  there  might  get  the 
benefit  of  a  little  fresh  air.  This  was  discontinued  after 
about  7  months,  but  whether  because  it  was  inefficient  or 
because  the  public  ceased  to  complain  was  not  clear.  A 
second  fan  10  feet  in  diameter  was  connected  with  two 
brick  tubes  2  feet  in  diameter  and  one-third  of  a  mile  long, 
opening  at  Baker  Street,  but  here  again  the  fan  was  worked 
only  a  short  time.  Blow-holes  in  the  streets  with  gratings 
were  built  from  time  to  time. 

In  1871  the  management  changed  hands  and  the  applica- 
tion of  the  principles  of  fan  ventilation  as  used  in  mines 
was  considered.  Sir  Benjamin  Baker,  Past  President  of 
the  Institution  of  Civil  Engineers,  after  a  careful  study  of 
the  air  currents  produced  by  outside  atmospheric  condi- 
tions and  by  the  trains,  calculated  that  to  properly  ventilate 
the  subway  with  fans  wTould  cost  about  half  as  much  as  to 
run  the  trains.  The  idea  was  to  exhaust  the  air  between 
stations  and  allow  it  to  flow  into  the  stations  from  outside. 


THE  AIR  OF  EUROPEAN  SUBWAYS  75 

A  large  number  of  experiments  and  calculations  were 
made  to  determine  to  what  extent  fans  could  be  used,  but 
it  was  always  shown  that  the  continuous  expense  of  operat- 
ing fans  would  make  them  impracticable. 

Following  ideas  successfully  employed  in  mines  consider- 
able sums  were  spent  in  dividing  the  road  into  two  parts. 
It  was  also  proposed  to  remove  the  foul  air  produced  by 
the  locomotives  by  drawing  it  down  into  exhaust  tubes 
placed  between  the  rails.  None  of  these  schemes  proved 
successful. 

Natural  ventilation.  Natural  currents  of  air  passing 
from  one  station  to  another  in  this  subway  were  observed 
running  in  velocity  up  to  4J  miles  per  hour,  as  measured 
with  anemometers.  The  amount  of  air  passing  out  of  a 
shaft  without  fan  ventilation  was  very  large.  In  one  case 
171,000  cubic  feet  of  air  per  minute  passed  out  of  two 
shafts,  one  14  feet  6  inches  in  diameter  and  the  other  16 
feet  in  diameter. 

Through  a  blow-hole  about  240  feet  in  area  at  Chalton 
Street  air  flowed  at  the  rate  of  from  3  to  5  feet  per  second. 
This  action  was  due  to  the  movement  of  trains  and  lasted 
from  49  to  53  seconds,  an  outward  blast  always  being 
followed  at  once  by  an  inward  draught.  During  one  hour 
when  31  trains  passed  this  opening,  the  total  period  of 
inward  draught  was  34  minutes  and  16  seconds  and  the 
total  outward  draught  26  minutes  and  9  seconds. 

Condition  of  the  air.  The  air  was  described  as  commonly 
rilled  with  smoke  and  steam  and  very  unpleasant.  Analy- 
ses made  by  Dr.  Henry  Armstrong,  F.R.S.,  for  the  com- 
pany showed  that  the  carbonic  acid  sometimes  amounted 
to  as  much  as  65  parts  per  10,000  volumes.  The  coal  used 
at  the  time  of  the  official  investigation  was  analyzed  by 


76  THE   AIR  AND   VENTILATION   OF   SUBWAYS 

Dr.  Armstrong  and  described  by  him  as  an  exceedingly 
good  non-bituminous  coal,  containing  83.94  per  cent  of 
carbon,  8.4  per  cent  of  ash,  1.09  per  cent  of  total  sulphur 
and  .96  per  cent  of  volatile  sulphur.  The  amount  of 
volatile  sulphur  which  went  off  in  the  form  of  sulphurous 
acid  was  below  one  per  cent. 

Analyses  of  the  air  made  by  Dr.  Haldane  of  the  Com- 
mittee gave  a  maximum  of  89  parts  of  carbon  dioxide. 
When  the  proportion  of  carbonic  acid  in  the  air  did  not 
exceed  15  parts  per  10,000,  Dr.  Haldane  considered  the  air 
"  good."  When  present  to  the  extent  of  20  parts  per 
10,000,  he  considered  it,  in  some  cases,  fairly  good.  Above 
this  it  was  bad. 

The  analyses  made  by  the  Committee  consisted  of  deter- 
minations of  carbonic  acid,  oxygen,  carbon  dioxide  and 
sulphurous  acids. 

The  attention  of  the  Committee  was  not  confined  to  the 
Metropolitan  Railway,  but  samples  of  air  were  taken  for 
analysis  from  other  tunnels  by  way  of  comparison.  The 
total  number  of  samples  collected  was  148. 

The  proportion  of  carbonic  acid  varied  from  a  minimum 
of  3  to  a  maximum  of  89.  The  variation  was  found  to 
depend  largely  on  the  state  of  the  wind,  the  movements  of 
trains  and  the  extent  to  which  the  subway  was  open  to  the 
outside  air. 

The  oxygen  was  deficient  in  the  mean  proportion  of 
119.4  parts  for  every  100  parts  of  excess  of  carbonic  acid 
(over  the  proportion  in  fresh  air).  In  individual  samples 
there  were  only  slight  variations  from  this  ratio. 

Carbon  dioxide,  due  to  imperfect  combustion  of  coal, 
was  present  in  very  appreciable  quantities.  Usually  there 
was  one  part  of  carbon  dioxide  to  13  parts  of  carbonic  acid 
(as  impurity).  This  proportion  was  fairly  constant. 


THE  AIR  OF  EUROPEAN  SUBWAYS  77 

Sulphurous  acid  was  present  in  the  average  ratio  of  one 
volume  for  every  440  of  carbonic  acid.  The  moisture  on 
the  walls  of  the  tunnel  and  water  standing  in  pools  gave  a 
marked  acid  reaction  with  litmus  paper  and  a  sample  of 
this  water  gave  with  barium  chloride  a  precipitate  of 
barium  sulphate  showing  the  presence  of  sulphuric  acid. 
Everything  capable  of  corrosion  in  the  subway  appeared 
to  be  acted  upon  by  the  acid,  including  the  leather  in  the 
boots  and  shoes  of  the  employees. 

The  Committee,  after  careful  consideration,  were  satis- 
fled  that  the  proportion  of  carbonic  acid  was  a  fair  measure 
of  the  more  dangerous  impurities  in  the  tunnel  air  and 
were  of  opinion  that  the  maximum  measure  of  permissible 
impurity  should  be  fixed  at  from  15  to  20  parts  of  carbonic 
acid  per  10,000  volumes  of  air  when  the  outside  air  was 
normal. 

Health  of  employees.  So  far  as  health  was  concerned, 
it  appeared  that  no  evil  effects  were  experienced  by  the 
engine  drivers,  firemen  and  uniformed  staff  of  employees. 
A  list  of  over  1000  men  all  of  whom  had  worked  5  years  or 
more  was  supplied  by  the  company.  For  the  seven  years, 
1890-6,  the  death  rate  among  the  employees  had  been 
11.2  per  1000,  while  for  London  it  was  19.5  and  for  36 
towns  of  England  19.8.  The  annual  average  number  of 
days'  absence  from  sickness  ranged  from  7.29  in  1890  to 
1 1 .26  in  1895.  The  time  lost  through  sickness  was  generally 
a  little  longer  among  drivers  and  firemen  than  among 
members  of  the  uniformed  force. 

Methods  of  ventilation  studied  by  the  Committee.  Two 
principal  methods  of  improving  the  air  were  considered  by 
the  Committee  as  a  result  of  its  studies:  (a)  removal  by 
means  of  fans;  (b)  additional  openings. 


78  THE   AIR  AND   VENTILATION   OF   SUBWAYS 

It  was  recognized  by  the  Committee  that  the  conditions 
in  the  Metropolitan  subway  were  quite  different  from  those 
which  obtained  in  mines  where  fans  were  successfully  used. 
The  subway  was  virtually  a  series  of  tunnels  in  short 
lengths.  At  their  ends  they  were  exposed  to  the  action  of 
winds.  Moreover,  the  air  was  subject  to  the  action  of 
trains  which,  in  the  Committee's  opinion,  acted  like  ill- 
fitting  pistons  in  a  cylinder,  continually  churning  up  and 
reversing  the  movements  of  air.  It  was  believed  that 
these  conditions  would  materially  interfere  with  the 
effective  action  of  fans  unless  the  latter  were  made  of 
extremely  large  dimensions.  There  was,  further,  the 
objection  that  the  action  of  fans  might  cause  enough 
vibration  to  produce  a  nuisance  to  property  holders  in  the 
neighborhood  of  the  road.  Finally,  it  appeared  certain 
that  the  fumes  extracted  from  the  tunnel  would  be  objec- 
tionable unless  discharged  at  a  considerable  height  above 
the  street  pavement. 

One  advantage  in  the  use  of  fans,  if  employed  according 
to  the  advice  of  those  who  advocated  them,  was  that  they 
would  improve  the  air  at  the  stations  where  the  maximum 
of  inconvenience  was  felt.  This  would  be  the  reverse  of 
the  conditions  which  obtained  at  first.  The  idea  was  to  so 
place  the  fans  between  stations  as  to  exhaust  the  air  from 
each  direction. 

The  existing  system  of  ventilation  by  openings  or  blow- 
holes was  considered  by  the  Committee  to  be  unsatis- 
factory both  to  persons  using  the  line  and  to  the  public 
using  the  streets  where  the  openings  existed.  But  it 
appeared  that  a  very  considerable  change  of  air  was  affected 
by  large  ventilating  openings.  Stations  provided  at  each 
end  with  adequate  blow-holes  were  much  less  uncom- 
fortable than  others. 


THE  AIR  OF  EUROPEAN  SUBWAYS  79 

A  special  point  of  objection  was  raised  against  the  dis- 
charge of  foul  gases  at  or  about  the  street  level,  both  on 
grounds  of  public  health  and  because  it  would  deteriorate 
the  value  of  neighboring  property. 

The  Committee  was  convinced  that  pure  air  could  best 
be  obtained  with  certainty  by  changing  the  motive  power 
to  electricity,  but  objection  to  this  change  was  made  by 
the  operating  companies  on  the  ground  that  they  could  not 
get  a  reliable  firm  or  combination  to  undertake  the  work 
of  electrification.  It  was  noted,  however,  by  the  Com- 
mittee at  this  time  that  the  Liverpool  Overhead  Railway 
tunnel,  half  a  mile  in  length,  was  being  operated  by  elec- 
tricity with  excellent  results,  both  as  to  economy  and  con- 
dition of  the  air,  and  the  future  electrification  of  the  road 
was  clearly  anticipated. 

Final  conclusions  of  the  Committee.  The  final  con- 
clusions of  the  Committee  were  that  the  most  satisfactory 
way  to  deal  with  the  ventilation  of  the  subway  would  be  to 
change  the  motive  power  to  electric  traction.  Failing 
this,  it  would  be  practicable  to  ventilate  it  satisfactorily  by 
means  of  fans  placed  at  points  intermediate  between  the 
stations;  but  the  cost  of  doing  this  would  be  considerable. 
Ventilation,  especially  at  the  stations,  would  be  sensibly 
improved  by  providing  more  openings  or  blow-holes  in  the 
roof.  But  satisfactory  results  meant  a  large  increase  in 
the  number  of  openings. 

In  view  of  the  fact  that  electric  traction  would  probably 
be  adopted  in  the  near  future,  the  Committee  recommended 
as  a  temporary  measure  the  construction  of  additional 
openings  with  the  understanding  that  if  electric  traction 
was  not  adopted  within  three  years,  the  blow-holes  should 
be  closed. 


80  THE   AIR  AND    VENTILATION   OF   SUBWAYS 

THE  PARALLEL  TUBES  OF  THE  CENTRAL  LONDON 
RAILWAY. 

The  Central  London  Railway  was  opened  for  traffic  in 
1900  and  belongs  to  the  type  of  deep  tunnels,  or  tubes,  of 
which  London  has  several  examples.1 

Construction.  These  tubes  are  circular  in  section,  lined 
with  cast  iron  and  lie  at  a  depth  of  from  40  to  100  feet  below 
the  street  level.  Between  stations  their  diameter  is  about 
11J  feet ;  at  the  stations  the  diameter  is  about  21  feet.  They 
are  operated  by  electric  power.  Two  lines  of  tunnel  are 
built,  each  to  accommodate  a  single  track.  Passengers 
enter  the  trains  at  the  stations  from  platforms  300  to  400 
feet  long  reached  by  elevators  or,  as  they  are  called  in 
England,  lifts.  It  is  through  these  passageways  that  ven- 
tilation is  expected  to  take  place. 

Method  of  ventilation.  Circulation  of  air  is  produced 
chiefly  by  the  piston  action  of  the  trains.  The  cross  sec- 
tion of  the  train  nearly  fills  that  of  the  tunnel  between 
stations.  During  the  busiest  hours  of  the  morning  and 
afternoon,  trains  are  run  about  every  two  minutes.  The 
number  of  passengers  carried  exceeds  23,000,000  per  year. 
The  average  number  of  passengers  carried  per  train  is  203. 

Owing  to  what  seemed  to  be  insufficient  means  of  venti- 
lation due,  no  doubt,  in  part,  to  a  consideration  of  the  great 
depth  of  the  road  below  the  surface  of  the  earth  and  to  the 
fact  that  the  tubes  were  connected  with  one  another  at 
frequent  intervals  thus  interfering,  to  some  extent,  with 

1  For  an  account  of  this  and  other  underground  railways  in  Great 
Britain  see  Mott  &  Hay  —  Proc.  International  Engineering  Congress, 
St.  Louis,  Mo.,  U.  S.  A.,  1904,  Trans.  Am.  Soc.  C.  E.,  Vol.  54.,  Part  F, 
p.  325. 


THE  AIR  OF  EUROPEAN  SUBWAYS  81 

the  movement  of  the  air  in  and  out  of  the  passages  and 
above  all  to  unpleasant  odors,  passengers  have  com- 
plained that  the  subway  was  not  sufficiently  ventilated. 

In  1901  the  air  of  the  Central  London  was  made  the 
subject  of  investigation  by  Dr.  H.  Wynter  Blyth,  Medical 
Officer  for  the  Borough  of  St.  Marylebone,  who  embodied 
his  results  in  a  presidential  address  which  he  delivered 
before  the  Incorporated  Society  of  Medical  Officers  of 
Health. 

Dr.  Blyth's  conclusion  was  that,  so  far  as  respiratory 
impurities  were  concerned,  the  air  of  the  tube  was  not 
seriously  vitiated.  The  analytical  results  showed  that  the 
general  air  of  the  Central  London  contained  8.7  to  10.7 
volumes  of  carbon  dioxide  per  10,000  volumes  of  air.  The 
outside  air  varied  from  3.7  to  6.2. 

Notwithstanding  these  reassuring  facts,  there  was  much 
popular  dissatisfaction  with  the  conditions  arid,  owing  to 
complaints  by  the  public,  the  London  County  Council 
undertook  to  thoroughly  investigate  the  condition  of  the 
air  in  1902.  The  Council  called  to  its  assistance,  as  experts, 
Dr.  Frank  Clowes,  Chief  Chemist;  Dr.  Shirley  Murphy, 
Medical  Officer  of  Health;  and  Dr.  Frederick  W.  Andrewes, 
Bacteriologist. 

Chemical  conditions.  Between  March  arid  October, 
1902,  118  samples  of  air  were  collected,  94  of  which  were 
analyzed  chemically  and  24  bacteriologically.  The  highest 
proportion  of  carbon  dioxide  was  14.7  volumes  per  10,000 
volumes  of  air;  this  was  present  in  the  air  of  a  passenger 
carriage.  The  smallest,  9.6,  was  in  an  empty  carriage. 

About  22  per  cent  of  the  samples  contained  less  than 
twice  as  much  carbon  dioxide  as  that  found  in  the  outside 
air  and  34  per  cent  contained  less  than  2J  times  as  much  as 


82  THE  AIR  AND   VENTILATION   OF   SUBWAYS 

the  carbon  dioxide  outside.  Nearly  all  the  samples  seem 
to  have  been  taken  near  noon  and  in  only  one  instance 
apparently  were  more  than  two  taken  on  a  single  day. 

The  air  between  stations  ranged  from  8.2  to  10.4  parts  of 
carbon  dioxide  per  10,000  volumes  of  air.  The  air  in  the 
lifts  contained  7.4  to  15.2  and  the  carriages  between  9.6  and 
14.7  parts.  The  outside  atmosphere  contained  from  3.0 
to  4.7  parts  of  carbon  dioxide. 

Samples  taken  on  three  other  London  underground  roads 
during  this  investigation  contained  from  7.6  to  28.8  volumes 
of  carbon  dioxide  per  10,000. 

Bacteriological  conditions.  The  bacteriological  work 
confirmed  the  results  obtained  in  the  chemical  analyses. 
Twelve  samples  of  air  from  the  subway  were  examined  and 
compared  with  the  results  of  twelve  samples  of  air  from  the 
streets. 

So  far  as  numbers  were  concerned,  the  results  corre- 
sponded closely  with  the  conditions  shown  by  the  carbon 
dioxide  analyses  made  of  samples  of  air  collected  at  the 
same  time.  There  was  a  direct  correspondence  between  the 
concentration  of  passengers  and  the  number  of  micro- 
organisms in  the  air. 

For  the  fresh  air  of  London,  Dr.  Andrewes  in  this  inves- 
tigation found  608  bacteria  per  cubic  meter  of  air  capable 
of  growing  on  an  agar  culture  medium  at  body  temperature 
and  ten  times  this  number  on  gelatin  at  room  temperature. 

Rather  more  bacteria  were  found  in  the  tunnel  air  than 
in  fresh  air  samples,  the  average  being  8820  per  cubic 
meter,  the  minimum  2800  and  the  maximum  20,600.  It 
is  interesting  to  observe  that  the  excess  in  numbers  of  bacte- 
ria in  the  subway  over  those  in  the  street  was  found  to  be 
due  to  non-pathogenic  sarcinse  and  allied  harmless  species. 


THE  AIR  OF  EUROPEAN  SUBWAYS  83 

Much  pains  was  taken  to  identify  the  species  of  bacteria 
present,  but  with  results  which  were  only  comparatively 
satisfactory  from  a  practical  standpoint.  The  species 
found  were  in  the  main  identical  with  those  which  occurred 
in  freslv  outside  air.  No  harmful  kinds  could  be  dis- 
covered. The  proportion  of  molds  to  bacteria  was  1  to  62. 

Conclusions.  The  investigation  led  to  the  opinion  that 
the  air  of  the  Central  London  Railway  was  not  far  dif- 
ferent from  that  of  inhabited  rooms  generally. 

At  the  time  of  these  studies  it  was  proposed  to  flush  out 
the  air  from  end  to  end  at  night  at  the  hours  of  minimum 
traffic  and  a  system  has  since  been  adopted  to  accomplish 
this  result.  In  the  summer  of  1905  automatic  check 
valves  were  also  in  use  to  regulate  the  flow  of  air  produced 
by  the  action  of  the  trains. 

CITY  AND  SOUTH  LONDON  RAILWAY 

In  1903  an  investigation  of  the  air  of  the  City  and  South 
London  Railway  was  made  by  Dr.  Scott  Tebb,  public 
analyst  of  South wark.1  This  was  the  first  deep  tube 
subway  in  London  and  at  the  time  of  this  investigation 
had  been  in  operation  12  years.  The  carbon  dioxide 
analyses  gave  the  following  results:  In  the  tubes,  7.9;  in 
the  carriages  in  the  tubes,  7.9;  and  in  the  streets,  3.8. 

Bacteria  were  determined  by  exposing  Petri  dishes  con- 
taining agar  culture  medium  which  was  later  incubated 
for  24  hours.  The  number  of  bacteria  which  settled  from 
the  air  and  were  subsequently  counted  were :  in  the  tunnel 
57  per  square  foot  per  minute,  in  railway  carriages  109  and 

1  Report  of  Public  Analyst  of  Southwark  on  the  Condition  of  the 
Air  of  the  City  and  South  London  Railway,  1903,  W.  Scott  Tebb,  M.D. 


84          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

in  the  streets  209.    The  fact  that  fewer  bacteria  were  found 
in  the  subway  than  in  the  streets  is  very  interesting. 

THE  METROPOLITAN  RAILWAY  OF  PARIS1 

The  underground  railways  of  the  Metropolitan  railway 
of  Paris  were  built  as  the  result  of  a  law  passed  in  1898 
which  provided  for  an  elaborate  subway  system  to  be 
operated  by  electricity.  The  construction  has  been 
carried  on  by  the  city.  For  operation  the  road  has  been 
leased  for  a  term  of  thirty-five  years  to  the  Compagnie  du 
Chemin  de  fer  Metropolitain  de  Paris.  The  plan  calls  for 
eight  lines  of  a  total  length  of  47.74  miles.  In  1907  the 
total  length  completed  and  in  use  was  27.62  miles. 

The  road  is  double  tracked  with  a  railway  gauge  of  4.72 
feet.  The  width  of  the  cars  is  7.8  feet.  A  clearance  of 
1.64  feet  is  provided  between  passing  cars  and  a  clearance 
of  2.3  feet  is  required  between  cars  and  side  walls.  The 
standard  section  is  formed  by  an  elliptical  arch  having  a 
width  of  23.3  feet  and  a  rise  of  6.79  feet  supported  by  two 
side  walls  9.54  feet  high  finished  inside  by  circular  arcs. 
The  total  inside  height  is  17.6  feet  and  the  width  at  the 
rail  level  is  21.65  feet. 

A  standard  station  comprises  two  side  platforms  246 
feet  long  and  13.4  feet  wide.  The  stations  are  reached  by 
staircases  opening  on  the  streets  and  emerging  through  the 
sidewalks  without  coverings.  The  staircases  have  straight 
flights  and  a  width  of  from  9.8  to  11.4  feet;  they  lead  down- 
ward into  rooms  where  the  tickets  are  sold.  From  the 
ticket  rooms  passengers  reach  the  nearer  platform  by 
another  staircase  9.22  feet  wide,  and  the  further  platform 
by  a  similar  staircase,  after  crossing  the  railway  tracks  by " 
means  of  a  foot  bridge  9.8  feet  wide. 

1  Biette,  The  Metropolitan  System  of  Paris,  Trans.  Am.  Soc.  C.  E., 
Vol.  54,  pp.  301-324. 


THE  AIR  OF  EUROPEAN  SUBWAYS  85 

The  masonry  used  is  almost  exclusively  cement  mortar 
and  concrete.  Inside  the  stations  the  walls  are  covered 
with  white  tiles  or  enameled  bricks. 

The  tunnels  of  the  Metropolitan  system  run  as  near  as 
possible  to  the  surface  of  the  streets.  In  places  the  road 
emerges  from  below  ground  and  follows  an  overhead 
structure,  and  where  it  has  been  necessary  to  cross  the 
Seine  River,  deep  tunnels  or  bridges  have  been  constructed. 

The  subway  carries  large  numbers  of  passengers  and 
trains  run  frequently.  In  the  first  year  55,900,000  people 
were  transported  and  in  the  next  year  over  72,000,000. 

Facts  concerning  the  provisions  for  ventilation  have  been 
kindly  furnished  by  M.  F.  Bienvenue,  Ingenieur  en  chef 
des  Fonts  et  Chaussees,  chef  du  Service  Technique  du 
Metropolitain.  No  general  system  either  of  mechanical 
ventilation  or  by  blow-holes  was  provided,  it  having  been 
believed  by  the  French  authorities  that  such  arrangements 
were  limited  in  effect  to  the  localities  where  they  are 
placed.  Fans  and  blow-holes  have  been  found  of  value, 
however,  in  a  number  of  instances  and  some  have  been 
constructed  and  others  are  contemplated. 

On  one  part  of  Line  No.  1  which  runs  across  the  center 
of  Paris  under  the  rue  de  Rivoli  and  the  Champs  Elysee, 
two  openings  have  been  made  which  have  produced  much 
improvement.  Also  six  similar  openings  have  been  es- 
tablished near  the  beginning  of  this  line.  Here,  however, 
it  is  not  the  subway  proper  but  a  lateral  gallery  which  is 
used  for  the  storage  of  cars  and  to  accommodate  an  electric 
sub-station  that  is  ventilated  in  this  way.  It  is  proposed 
to  open  six  more  blow-holes  to  the  outside  air  in  the  stations 
on  Line  No.  1. 

On  Line  No.  2,  which  passes  in  a  semi-circular  way 
through  the  northern  part  of  the  city,  a  ventilating  fan  has 


86          THE  AIR  AND   VENTILATION  OF   SUBWAYS 

been  installed  in  a  chamber  near  the  western  terminal  of 
the  line  where  the  road  is  unusually  deep.  Another 
chamber  with  a  ventilating  shaft  is  installed  at  another 
point  on  this  line  and  is  to  receive  a  fan  also.  Two  large, 
additional  openings  are  proposed  on  the  boulevard  des 
Batignolles  and  boulevard  Belleville.  At  the  Place  de  la 
Nation  at  the  head  of  a  terminal  loop  of  the  line,  still 
another  ventilating  shaft  exists.  Finally,  it  is  proposed 
to  establish  a  second  shaft  a  short  distance  from  the  last 
mentioned  and  still  one  more  at  the  Place  de  la  Nation. 

On  the  southern  half  of  this  circular  line  the  conditions 
of  ventilation  are  particularly  favorable.  There  are  there 
only  two  openings  for  ventilation,  one  at  the  Place  d'ltalie 
over  a  small  loop.  It  is  proposed  to  make  an  opening  at 
the  boulevard  Edgar-Quinet  over  a  storage  siding  near  the 
principal  line. 

On  Line  No.  5,  a  short  piece  of  road  running  across  the 
city  in  a  generally  north  and  south  direction,  it  is  proposed 
to  construct  six  openings  to  the  outside  air;  one  of  these 
is  to  eventually  receive  a  fan. 

On  Line  No.  3,  the  remaining  section  of  the  Metropoli- 
tan system  in  operation  in  1907,  two  shafts  are  arranged 
with  a  view  to  receiving  ventilating  fans  for  the  loop  which 
exists  at  the  terminus  of  this  line  near  the  Park  Monceau. 
One  other,  with  a  fan,  exists  at  the  opposite  extremity  at  a 
branch  which  serves  for  the  storage  of  cars.  Three  other 
openings  are  proposed,  one  for  each  of  three  important 
stations;  one  of  these  is  to  be  provided  with  a  fan. 

Studies  of  the  air  of  the  Metropolitan  were  begun  on  the 
16th  of  January,  1901,  about  six  months  after  the  first 
section  of  the  road,  known  as  Line  No.  1,  was  put  in  service.. 
At  a  later  period,  Line  No.  1  and  the  other  lines  as  they 
have  been  successively  opened  have  been  put  under  syste- 


THE  AIR  OF  EUROPEAN  SUBWAYS  87 

matic  observation  as  to  their  temperature,  humidity,  and 
the  chemical  composition  of  the  air.  This  work  has  been 
done  by  the  Montsouris  Municipal  Laboratory.  The 
analysts  hi  charge  have  been  Messrs.  Albert-Levy  and  A. 
Pecoul.  Frequent  reports  have  been  made  by  these  gentle- 
men to  the  Director  of  the  Public  Works.  It  is  to  the 
courtesy  of  the  gentlemen  in  charge  of  these  investigations 
and  to  their  official  reports  that  the  following  data  are 
chiefly  due. 

At  least  twice  a  year,  at  times  corresponding  to  the  hot 
and  cold  seasons,  the  investigators  have  visited  the  different 
parts  of  the  lines  to  take  samples  of  the  air,  the  hour  chosen 
usually  being  between  3  and  4  o'clock  in  the  afternoon. 
The  samples  of  air  have  been  taken  for  analysis  in  rubber 
pouches  of  a  capacity  of  about  15  liters.  These  samples 
have  been  transported  to  the  laboratory  for  examination. 

In  sections  of  most  interest,  automatic  apparatus  has 
also  been  set  up  to  show  the  chemical  composition  of  the 
air  during  an  entire  day  and  during  the  day  and  night 
respectively. 

In  addition  to  the  analysis  of  air,  anemometers  have 
been  used  to  study  the  velocity  of  draughts  and  currents. 

It  has  been  found  that  the  air  improves  materially  during 
the  night  when  no  trains  are  operated,  but  when  the  road 
is  put  in  service  in  the  morning,  the  carbon  dioxide  increases 
rapidly.  In  the  general  air  of  the  subway  the  carbon 
dioxide  has  been  found  to  be  generally  below  9  parts  per 
10,000  and  seldom  above  16. 

During  the  months  of  August  and  September,  the  pro- 
portion of  carbon  dioxide  is  notably  less  than  at  other 
seasons  of  the  year,  the  result,  no  doubt,  of  the  fact  that 
the  doors  at  the  stations  are  then  open  and  the  number  of 
passengers  not  as  large  as  at  other  seasons.  In  the  cars  the 


88          THE  AIR  AND  VENTILATION  OF  SUBWAYS 

carbon  dioxide  has  seldom  been  found  above  16  parts  per 
10,000. 

In  the  opinion  of  the  investigators,  the  discomfort  which 
is  sometimes  experienced  in  the  Metropolitan  is  due  to  the 
high  temperature,  the  large  amount  of  moisture  and  the 
amount  of  carbon  dioxide  present.  In  their  opinion,  taken 
alone,  none  of  these  factors  would  be  likely  to  produce  any 
discomfort,  but  together  they  produce  sensations  which 
are  universally  objected  to. 

The  temperature  inside  of  the  cars  does  not  vary  greatly. 
It  is  practically  like  the  temperature  outside  of  the  cars. 
In  winter  when  the  temperature  of  the  air  in  the  streets 
descends  to  the  neighborhood  of  zero,  it  is  +  20  degrees  in 
the  cars.  In  summer,  when  the  temperature  out  of  doors 
is  20  degrees,  the  cars  range  between  22  and  25  degrees. 

The  average  temperature  of  the  subway  in  the  warm 
season  during  the  years  1904-5-6  has  been  20.5  degrees  and 
19  degrees  during  the  cold  season. 

The  air  of  the  stations  has  been  found  to  contain  variable 
proportions  of  carbon  dioxide,  depending  upon  the  com- 
position of  the  air  of  the  adjacent  tunnels,  the  number  of 
passengers  and  the  frequency  with  which  the  doors  at  the 
entrances  and  exits  are  opened. 

In  1903  it  was  noticed  that  black  dust  was  soiling  the 
walls  of  the  tunnels  and  the  opinion  was  expressed  that 
this  dust  might  be  injurious  to  the  employees  of  the  road 
who  were  required  to  work  between  the  stations.  The 
dust  adheres  to  the  walls  and  rails.  It  is,  moreover, 
regarded  as  inflammable  as  tinder.  It  has  interfered 
with  the  insulation  of  the  electric  current. 

The  investigators  are  of  opinion  that  the  exchange  of 
air  which  occurs  between  the  subway  and  streets  during 
the  night  is  sufficient,  but  that  that  which  occurs  in  the 


THE  AIR  OF  EUROPEAN  SUBWAYS  89 

day  is  insufficient  for  ventilating  purposes.  As  a  result  of 
the  circulation  produced  by  the  trains,  the  amount  of 
carbon  dioxide  increases  and  is  distributed  through  the 
tunnels  until  it  renders  the  whole  atmosphere  unwhole- 
some, as  measured  by  a  standard  raised  by  a  commission 
on  hygiene  appointed  by  the  French  Minister  of  Commerce. 
This  standard  requires  that  when  air  contains  more  than 
10  parts  of  carbon  dioxide  as  a  result  of  its  being  used  for 
breathing,  it  is  to  be  considered  unsatisfactory. 

It  might  be  supposed  that  the  circulation  of  the  trains 
would  produce  a  useful  amount  of  ventilation,  but  the 
investigators  were  of  opinion  that  this  was  not  true. 
Experiments  with  anemometers,  they  thought,  proved  that 
the  displacement  produced  by  the  passage  of  trains  caused 
only  an  agitation  of  the  air  and  that  as  soon  as  the  train 
passed  this  agitation  ceased. 

The  draughts  of  air  were  considered  not  only  uncom- 
fortable but  dangerous  at  some  of  the  entrances  and  exits 
of  the  stations.  Although  they  seemed  to  some  persons 
to  indicate  the  displacement  of  a  great  deal  of  air,  this 
displacement  seemed  to  the  investigators  to  be  in  reality 
very  little;  in  fact  only  sudden  energetic  gusts  and  without 
effect  upon  the  chemical  composition  of  the  air  of  the 
subway. 

Notwithstanding  these  unfavorable  opinions,  however, 
the  analysts  have  found  that  blow-holes  do  produce  .bene- 
ficial effects  upon  the  composition  of  the  air.  The  construc- 
tion of  some  openings  has  been  followed  by  a  reduction  in 
the  carbon  dioxide  in  the  vicinity  from  9.2  to  6.8  in  one 
case,  from  9.5  to  6.4  in  another,  from  10.3  to  6.1  in  a  third, 
and  from  11.4  to  6.5  in  a  fourth.  Nor  did  they  find  that 
the  improvement  was  limited  strictly  to  the  immediate 
neighborhood  of  the  openings.  Otherwise  it  is  difficult  to 


90          THE  AIR  AND   VENTILATION  OF  SUBWAYS 

understand  why  the  management  has  decided  to  extend 
this  method  of  relief  to  the  extent  indicated  in  the  first  part 
of  this  chapter. 

Elsewhere  it  has  been  remarked  that  the  temperature  of 
the  tunnels  was  generally  high  and  did  not  seem  to  vary 
much  with  the  temperature  of  the  outside  air,  but  it  is 
necessary  to  remark  that  the  ventilation  in  the  evening 
which  produces  a  notable  reduction  in  the  carbon  dioxide 
also  produces  a  slight  reduction  in  the  temperature  of  the 
tunnel.  For  example,  when  the  carbon  dioxide  in  the  day 
has  been  11.2  and  the  temperature  16.2  degrees,  it  has 
fallen  at  night  with  a  reduction  in  carbon  dioxide  of  5.1  to 
14.9  degrees. 

It  has  also  been  remarked  that  in  the  early  hours  of  the 
morning  before  the  tunnel  air  has  been  at  all  affected  by 
the  respiration  of  passengers  the  temperature  has  remained 
high  and  there  was  a  characteristic  odor.  The  investiga- 
tors think  that  this  odor  is  produced  by  organic  matter 
condensed  upon  the  walls  and  that  a  very  energetic  venti- 
lation would  be  necessary  to  dissipate  it.  If  it  is  necessary 
to  get  rid  of  these  odors  and  lower  the  temperature  it  will 
be  necessary,  in  the  opinion  of  the  French  experts,  to 
employ  some  special  process  of  refrigeration,  such,  for 
example,  as  have  been  used  in  certain  mountain  tunnels. 

RESULTS  OF  AN  INSPECTION  OF  EUROPEAN  SUBWAYS 

IN  1907 

Sensible  condition  of  the  air.  In  the  summer  of  1907 
the  author  made  careful  inspections  of  the  principal  sub- 
ways of  Europe,  including  those  of  London,  Paris  and 
Berlin,  at  the  request  of  the  Interborough  Rapid  Transit 
Company  of  New  York,  and  enjoyed  opportunities  to 
discuss  the  sanitary  features  of  subways  with  the  engineers 


THE  AIR  OF  EUROPEAN   SUBWAYS  91 

who  built  the  roads,  the  officials  who  are  operating  them 
and  with  chemists,  bacteriologists  and  health  officers  who 
are  interested  in  them  from  a  public  health  standpoint. 

Among  those  to  whom  the  author  is  indebted  for  cour- 
tesies in  this  direction  are  Mr.  William  Barclay  Parsons, 
New  York;  at  London,  Mr.  Eustace  Burrows,  Secretary 
Great  Northern  Railway;  Mr.  Granville  C.  Cuningham, 
General  Manager,  Central  London  Railway;  Mr.  Maurice 
Fitzmaurice,  Chief  Engineer,  London  County  Council ;  Mr. 
Frank  Clowes,  Chief  Chemist,  London  County  Council;  Mr. 
James  R.  Chapman,  General  Manager,  Metropolitan  Dis- 
trict Electric  Traction  Company,  Ltd.;  Mr.  Francis  Fox, 
Consulting  Engineer.  At  Liverpool,  Mr.  S.  B.  Cottrell, 
Engineer  and  General  Manager,  Liverpool  Overhead 
Railway  Company.  At  Birkenhead,  Mr.  J.  Shaw,  Resident 
Engineer,  Mersey  Railway  Company.  At  Paris,  Mr. 
Georges  Bechmann,  Consulting  Engineer,  and  M.  Bien- 
venue,  Chief  Engineer  of  the  Metropolitan  Railway.  At 
Berlin,  Herrn  A.  Lerche. 

There  were  considerable  differences  in  the  general 
appearance  of  the  subways  visited,  and  doubtless  in  their 
chemical  and  microbic  characters,  but  greater  differences 
in  the  sensible  condition  of  the  air.  There  was  more  or 
less  odor  about  all  of  them,  the  spacious  Blackwall  tunnel 
in  which  no  cars  are  operated  and  the  elaborately  ven- 
tilated Mersey  tunnel  not  entirely  excepted. 

Owing,  perhaps,  to  the  hot  weather,  the  Metropolitan 
of  Paris  was  more  open  to  the  outside  air  than  it  had 
previously  been,  the  doors  being  kept  open  at  the  stations 
most  of  the  time,  and  the  air  on  this  road  was  not  as 
unpleasant  as  reports  had  indicated. 

The  heat  was  nowhere  annoying,  but  the  air  was  humid 
and  odors  of  disinfectants  frequently  produced  the  involun- 


92          THE  AIR  AND   VENTILATION  OF   SUBWAYS 

tary  impression  that  the  air  was  not  as  good  as  it  could 
well  have  been  made. 

Some  of  the  long,  underground  passages  of  the  tube 
railways  were  draughty.  The  glazed  tile  linings  of  the 
stations  and  passageways  were  generally  kept  brightly 
polished  and  fairly  clean. 

Less  can  be  said  concerning  the  cleanliness  of  the  floors: 
they  were  often  only  superficially  clean.  A  surprisingly 
large  amount  of  wood  is  used  in  the  cars  and  on  the  station 
platforms  considering  the  inflammability  of  this  material 
and  its  capacity  for  absorbing  fluid  matters.  The  lighting 
of  the  stations  and  passageways  was,  on  the  whole,  ade- 
quate. 

Spitting  on  the  floors  was  not  as  prevalent  as  might  be 
expected  in  view  of  the  fact  that  smoking  is  allowed  on 
some  roads.  In  London  the  companies  recognize  that 
they  have  the  authority  to  regulate  this  practice  and  are 
trying  to  diminish  it. 

Some  cars  are  well  designed,  well  lighted  and  properly 
cleaned,  but  this  was  not  the  rule.  In  Paris  the  practice 
of  leaving  the  management  of  the  doors  partly  to  the 
public  seemed  dangerous. 

There  was  no  difficulty  about  ventilating  any  of  the 
cars.  In  fact  the  currents  of  air  in  the  subways  outside  of 
the  cars  is  so  strong  that  with  even  meagre  openings  it 
was  not  difficult  to  give  the  passengers  all  the  air  which 
they  will  stand. 

Roadbeds.  When  it  is  considered  that  the  fate  of  all 
dirt,  dust  and  other  harmful  solid  matters  which  are  not 
cleaned  up  and  carried  out  of  a  subway  is  to  get  upon  the 
roadbed  and  sink  into  it  or  be  blown  about  by  the  trains, 
it  would  seem  that  the  necessity  for  providing  for  thorough 


THE  AIR  OF  EUROPEAN  SUBWAYS  93 

cleanliness  in  all  parts  would  be  evident.  Yet  in  so  far  as 
the  sanitary  condition  of  roadbeds  is  concerned,  no  subway 
visited  was  wholly  satisfactory.  In  few  cases  was  it 
possible  to  give  the  whole  interior  the  thorough  cleansing 
which  the  needs  of  the  situation  demanded. 

Odor.  The  most  characteristic  feature  of  the  air  of 
every  subway  was  an  unpleasant  odor.  The  odor  was  not 
always  the  same  among  the  subways  visited  and  probably 
arose  from  different  causes  on  different  roads.  It  was 
interesting  to  observe  that  where  two  subways  were  con- 
nected underground,  separate  odors  were  noticeable. 
Doubtless  these  odors  would  have  given  some  indication  of 
the  mixture  of  air  which  was  taking  place  had  they  been 
studied  closely. 

The  odors  were  strongest  where  the  subways  were  damp 
and  warm.  The  oldest  roads,  and  particularly  those  which 
were  looked  after  least  carefully,  were  the  most  unpleasant. 

In  every  city  the  odors  of  the  subways  were  locally  con- 
sidered to  be  objectionable,  but  it  was  noticeable  that  these 
objections  had  nowhere  reached  such  a  point  as  to  bring 
about  a  thorough  investigation.  A  free  use  of  disinfectants, 
sprinkled  in  liquid  form,  seemed  to  be  the  chief  measure 
taken  to  overcome  the  odors.  A  careful  study  of  the  com- 
position of  the  disinfectants  and  the  ways  in  which  they 
were  used  gave  the  impression  that  they  were  more  likely 
to  add  to  the  difficulty  than  to  reduce  it.  On  one  road 
tons  of  disinfectants  had  been  used  without  producing  any 
beneficial  effect. 

Temperature.  There  was  considerable  difference  in  the 
temperature  of  different  subways.  The  shallow  roads 
were  cooler  than  the  deep  ones  and  the  new  were  cooler 


94  THE  AIR  AND   VENTILATION  OF   SUBWAYS 

than  the  old.  The  subways  which  were  least  open  to  the 
outer  air  and  in  which  the  greatest  amount  of  travel 
occurred  were  the  warmest. 

It  was  apparent  that  many  subways  were  becoming 
warmer  year  by  year.  The  newest  London  tubes  were 
from  7  to  10  degrees  cooler  than  the  older  roads  although 
the  latter  ran  in  the  same  clay  at  about  the  same  depth  and 
had  about  the  same  amount  of  travel.  Observations  by 
the  managers  showed  that  there  was  an  increase  of  about 
2  degrees  Fahrenheit  per  year  in  the  temperature  of  the 
new  tubes. 

Engineering  opinion  was  unanimous  concerning  the 
cause  of  the  heating.  It  is  due  to  the  heavy  traffic  and  to 
the  fact  that  the  capacity  of  the  walls  and  the  surrounding 
earth  to  absorb  heat  becomes,  with  the  passage  of  time, 
more  and  more  nearly  exhausted. 

The  air  in  the  Paris  Metropolitan  is  always  warm.  There 
is  no  doubt  that  the  masonry  is  carrying  away  the  heat  as 
rapidly  as  its  conducting  power  and  that  of  the  surround- 
ing earth  will  permit,  but  there  is  less  heat  escaping  through 
ventilation  than  is  common  in  other  shallow  subways. 

The  Berlin  subway  is  comparatively  cool.  The  road 
lies,  for  almost  its  whole  length,  in  ground  water,  and  for 
this  reason  the  heat  is  rapidly  conducted  away. 

The  heat  of  the  London  tubes  penetrates  to  a  consider- 
able depth  through  the  clay  which  surrounds  them.  Obser- 
vations of  temperature  beyond  the  tubes  of  the  Central 
London  Railway  made  by  Mr.  Granville  C.  Cuningham, 
General  Manager,  showed  that  at  a  depth  of  70  feet  below 
the  street  level,  the  temperature  of  the  earth  was  65  degrees 
Fahrenheit,  at  a  point  4  feet  behind  tunnel  linings  it  was  63 
degrees. 

The  air  of  foreign  subways  is  comparatively  dry  con- 


THE  AIR  OF  EUROPEAN  SUBWAYS 


95 


FIG.  11.  Weather  at  New  York  during  the  investigation.  Plotted  from 
data  of  U.  S.  Weather  Bureau.  Shaded  areas  in  circles  are  wind 
roses  and  show  direction  and  relative  movement  of  wind  from  each 
point  of  the  compass.  Heavy  black  lines  below  show  average  and 
greatest  velocity,  in  miles  per  hour,  of  wind.  Light  black  lines  to  the 
right  show  average  temperature  for  the  month  in  Fahrenheit  degrees, 


96          THE  AIR  AND   VENTILATION   OF   SUBWAYS 

sidering  the  large  amount  of  water  which  is  used  to  sprinkle 
the  floors  of  stations  and,  mixed  with  chemicals,  to  dis- 
infect the  tracks.  This  comparative  dryness  is  explainable 
by  the  fact  that  the  actual  amount  of  water  vapor  is  not 
small,  but  because  of  the  warmth  of  the  air,  the  humidity 
appears  low.  Places  exist  in  some  of  the  subways  which 
are  extremely  damp. 

Dust.  A  peculiar  kind  of  black,  metallic  dust  exists  in 
all  subways  operated  by  electric  traction  and  is  undoubtedly 
due  largely  to  the  wear  and  tear  of  the  machinery  of  the 
trains. 

The  amount  varies  in  different  roads  according  to  the 
number  and  speed  of  the  trains  and  other  circumstances, 
but  it  is  always  present  in  easily  detectable  quantities.  In 
the  Paris  subway  the  average  quantity  of  dust  produced 
is  0.7  U.  S.  ton  per  mile  of  subway  per  month  and  in  some 
parts  of  this  system  it  is  sometimes  in  excess  of  this  amount. 

An  effort  is  made  everywhere  to  remove  the  dust,  for 
it  is  regarded  as  disfiguring  to  the  linings  of  the  subways 
and,  more  important  still,  injurious  to  health  and  inflam- 
mable. It  has  caused  difficulty  with  electric  insulations, 
both  in  London  and  Paris. 

The  dust  is  generally  removed  from  the  walls  by  hand. 
One  of  the  objects  of  sprinkling  the  platforms  is  to  lay  the 
dust.  An  elaborate  apparatus  for  removing  the  dust  and 
disinfecting  the  walls,  roof  and  floor  is  employed  in  the 
Central  London  tube.  It  consists  of  a  spraying  apparatus 
mounted  on  a  car  and  provided  with  a  pump.  It  is  moved 
through  the  subway  at  night  and  sprinkles  the  whole 
perimeter  with  lime  disinfectant.  A  second  apparatus 
formed  like  a  large  funnel  is  mounted  on  another  car  which 
runs  behind  and  collects  the  dust  disengaged  by  the 


THE  AIR  OF  EUROPEAN  SUBWAYS  97 

sprinkler.  Three  of  the  London  roads  have  recently 
introduced  a  new  form  of  brake  block  which  is  said  to 
be  capable  of  reducing  the  formation  of  metallic  dust 
fully  80  per  cent. 

Molds.  Molds  appear  to  exist  in  practically  all  European 
subways  and  are  particularly  abundant  in  damp  places. 
One  whole  line,  several  miles  in  length,  appears  to  be 
badly  infested  with  these  unpleasant  organisms.  It  was 
said  to  be  impossible  for  the  management  of  this  road  to 
leave  a  car  at  the  end  of  a  siding  for  two  or  three  days 
without  visible  growths  of  molds  appearing  over  it. 

It  is  not  known  that  these  molds  are  actually  harmful 
to  health,  but  some  molds  are  so,  and  as  they  unquestion- 
ably produce  offensive  odors  and  are  objectionable  in 
other  respects,  it  seems  curious  that  no  measures  are  taken 
to  avoid  them. 

Ventilation.  Owing  to  continued  complaints  by  the 
public,  methods  of  improving  the  ventilation  have  been 
adopted  by  various  foreign  subways,  but  nowhere  has  so 
much  attention  been  given  to  this  subject  since  electric 
traction  came  into  use  as  in  New  York. 

The  author's  studies  of  English,  French  and  German 
subways  show  that  the  piston,  or  pumping,  action  of 
trains  is  of  great  value  in  ventilation.  In  fact  it  appears 
that  fans  and  other  mechanical  devices  are  rarely  necessary 
unless  to  improve  purely  local  conditions.  It  was  evident 
that  the  pumping  action  of  the  trains  was  not  so  complete 
in  the  deep  London  subways  as  in  roads  near  the  surface, 
but,  combined  with  the  action  of  elevators  at  the  stations 
and  the  draughts  through  stairways  and  shafts,  the  trains 
caused  an  immense  amount  of  air  to  pass  in  and  out. 

The  subway  at  Berlin,  which  is  of  the  same  type  as  those 


98          THE  AIR  AND   VENTILATION  OF  SUBWAYS 

of  New  York,  Paris  and  Boston,  is  well  ventilated.  The 
roof  is  close  to  the  surface  of  the  streets  and  the  stairways 
are  so  arranged  as  to  be  virtual  extensions  of  the  plat- 
forms, a  construction  which  permits  of  an  unobstructed 
flow  of  air  between  the  subway  and  the  streets.  Large 
shafts  have  been  built  to  serve  as  emergency  exits  and  these 
act  as  blow-holes. 

Health  of  employees.  The  health  of  employees  was 
inquired  into  without  finding  anywhere  an  excessive 
amount  of  illness  which  could  be  ascribed  to  subway  con- 
ditions. In  Paris  it  was  thought  that  rather  more  illness, 
such  as  colds,  occur  among  the  employees,  but  no  definite 
evidence  to  this  effect  could  be  gathered.  On  the  London 
Underground  Electric  Railways  which  include  the  Baker 
Street  and  Waterloo,  Great  Northern,  Piccadilly  and 
Brompton,  Charing  Cross,  Euston  and  Hempstead  Railways, 
there  are  only  about  0.5  per  cent  of  the  employees  away 
through  sickness  at  a  time.  Very  often  this  figure  drops  to 
zero. 

Through  the  courtesy  of  Mr.  Granville  C.  Cuningham,  the 
following  figures  were  obtained  to  show  the  amount  of 
sickness  among  the  500  employees  at  work  in  the  Central 
London  Railway.  The  following  percentages  refer  to  the 
month  of  September,  1907. 

Per  cent 

Inspectors,  station  masters  and  yard  masters      ....  3.3 

Signalmen 0.6 

Liftmen 2.5 

Ticket  collectors 3.0 

Guards  and  conductors 1.0 

Platform  men 3.2 

Average 2.3 

The  nature  of  the  sicknesses  is  not  known.  Accidents 
were  included  in  the  figures. 


CHAPTER  V 

THE  AIR  OF  THE  NEW  YORK  SUBWAY 

DOUBT  concerning  the  purity  of  the  subway  air  began  to 
occupy  the  public  mind  within  a  few  weeks  after  the  sub- 
way was  opened  in  October,  1904.  Some  analyses,  pur- 
porting to  have  been  made  in  a  simple  and  ready  way  by 
a  public  spirited  citizen  were  published  in  the  daily  press 
and  seemed  to  show  that  the  air  was  vitiated  to  an  alarming 
extent.  The  accuracy  of  these  tests  was  challenged  by 
competent  chemists,  but  public  anxiety,  once  aroused,  was 
not  easily  to  be  set  at  rest. 

At  this  point  Dr.  Charles  F.  Chandler,  Professor  of 
Chemistry  at  Columbia  University  and  Consulting  Hygien- 
ist  to  the  New  York  City  Department  of  Health,  undertook 
a  series  of  careful  determinations  of  the  carbon  dioxide 
and  oxygen  in  different  parts  of  the  subway  and  at  dif- 
ferent times  of  the  day.  By  these  tests  the  carbon  dioxide 
was  not  found  to  be  excessive  nor  the  oxygen  depleted. 
Dr.  Chandler  reached  the  opinion  that  the  subway  air  was 
exceedingly  good.  The  results  of  these  investigations  were 
published  in  the  annual  reports  of  the  Rapid  Transit 
Commission  and  were  issued  separately  in  pamphlet  form. 

The  author's  investigations  were  begun  in  the  summer 
of  1905  for  the  Board  of  Rapid  Transit  Commissioners  for 
the  City  of  New  York  and  extended  continuously  for  six 
months.  The  original  data,  largely  in  tabulated  form, 
were  transmitted  to  the  Commissioners  in  February,  1906. 

It  was  through  the  intelligent  and  skillful  efforts  of 


100          THE  AIR  AND   VENTILATION  OF  SUBWAYS 

persons  who  were  called  upon  to  aid  in  the  investigation 
that  the  results  were  in  large  part  due.  The  average 
number  of  assistants  continuously  engaged  on  the  work 
was  ten.  From  first  to  last,  there  were  twenty-one  persons 
officially  connected  with  the  investigation;  about  two- 
thirds  of  this  number  were  technical  school  graduates. 

Capable  work  was  done  by  Floyd  J.  Metzger,  Ph.D.,  in 
the  chemical  analyses;  by  Clinton  B.  Knapp,  M.D.,  and 
Payne  B.  Parsons,  M.D.,  in  the  bacteriological  studies;  and 
by  George  S.  Frost,  C.E.,  in  the  meteorological  observa- 
tions. Aid  of  an  unusually  competent  character  was  given 
in  the  studies  of  ventilation  and  in  compiling  the  data  by 
Mr.  John  P.  Fox. 

Valuable  counsel  and  other  assistance  was  given  by  a 
number  of  the  author's  friends  who  were  not  officially 
connected  with  the  investigation.  Most  of  these  persons 
were  professors  in  Columbia  University.  Among  them 
may  be  mentioned  Dr.  Charles  F.  Chandler,  Professor  of 
Chemistry;  Dr.  T.  Mitchell  Prudden,  Professor  of  Path- 
ology; Dr.  William  Hallock,  Professor  of  Physics;  and  Dr. 
Philip  Hanson  Hiss,  Professor  of  Bacteriology.  To  these 
and  others  whose  help  added  accuracy  and  value  to  the 
investigation,  the  author  desires  to  express  his  sense  of 
appreciation  and  thanks. 

SCOPE  OF  THE  INVESTIGATION 

The  principal  questions  investigated  related  to  tem- 
perature, humidity,  odor,  bacteria,  and  dust.  The 
conditions  found  in  the  subway  were  compared  with  the 
conditions  found  in  the  streets  through  which  the  subway 
runs,  and  occasionally  with  conditions  in  other  places. 
The  weather  conditions  during  the  investigation  are  shown 
graphically  in  Fig.  11. 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  101 

In  seeking  to  explain  the  causes  of  the  conditions, 
it  was  necessary  to  take  account  of  the  sanitary  care 
which  the  subway  received  from  the  company  which 
operated  it  and  the  manner  in  which  ventilation  was 
accomplished. 

No  attempt  was  made  to  devise  a  comprehensive  system 
of  ventilation  or  cooling  to  improve  the  air.  Experiments 
in  this  direction  were  being  made  by  the  regular  engineering 
staff  of  the  commission.  The  author  merely  studied  the 
effects  of  these  experiments  and  reported  upon  them. 
The  details  of  these  ventilation  experiments  will  not  be 
given  here  but  it  may  be  said  that,  during  the  operation  of 
trains,  large  centrifugal  exhaust  fans  produced  no  visible 
effect  on  the  composition  of  the  air,  but  large  openings  in 
the  roof  gave  substantial  benefit.  A  necessary  and  suf- 
ficient amount  of  opening  for  each  section  of  the  subway 
was  clearly  indicated  and  determined  by  the  author's 
investigations. 

In  all,  there  were  about  2,200  chemical  analyses  of  air, 
3,000  determinations  of  bacteria,  and  about  400  other 
analyses  in  special  studies  of  dusts,  oils,  disinfectants,  and 
other  substances.  About  50,000  separate  determinations 
of  temperature  and  humidity  were  made  prior  to  the 
adoption  of  a  system  for  automatically  and  continuously 
recording  temperatures  throughout  the  length  of  the 
subway  and  in  the  streets. 

The  methods  employed  in  studying  the  different  topics 
were,  for  the  most  part,  such  as  had  been  used  in  other 
sanitary  and  meteorological  investigations  in  which  a  con- 
siderable degree  of  accuracy  was  required.  It  is  not 
claimed  that  they  would  have  been  the  best  to  adopt  in  a 
purely  scientific  research.  It  was  necessary  to  design  them 
for  practical  as  well  as  accurate  use. 


102        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

For  the  most  part,  the  air  to  be  analyzed  was  collected 
at  an  elevation  of  18  inches  to  2  feet  above  the  pavement. 
This  height  was  decided  on  as  the  most  convenient  and 
suitable,  after  an  attempt  had  been  made  to  collect  it  at 
the  breathing  line.  Only  by  taking  samples  near  the 
ground  was  it  possible  to  avoid  attracting  curious  crowds 
of  persons  whose  presence  would  have  rendered  the  samples 
valueless.  Tests  made  of  air  from  different  elevations 
indicated  that  no  substantial  error  was  made  in  taking 
samples  near  the  pavement. 

Very  few  samples  of  air  were  taken  in  the  cars.  Persons 
familiar  with  the  conditions  of  crowding  in  the  cars  of  the 
New  York  subway  at  practically  all  hours  of  the  day  will 
appreciate  the  inconvenience  with  which  delicate  and  bulky 
scientific  apparatus  could  be  used  among  persons  standing 
as  close  together  as  it  was  physically  possible  to  stand. 
Furthermore,  the  question  at  issue  was  not  whether  the 
passengers  in  the  cars  obtained  good  air  or  not,  but  whether 
the  air  outside  the  cars  was  satisfactory.  The  samples  of 
car  air  analysed  showed  that  the  amount  of  ventilation 
was  usually  large  and  the  air  as  satisfactory  as  could  be 
expected  considering  the  crowding. 

ESSENTIALS  OF  CONSTRUCTION  AND  OPERATION  AT 
THE  TIME  OF  THE  INVESTIGATION 

The  details  of  construction  and  equipment  of  the  New 
York  subway  have  been  made  the  subject  of  so  many 
extended  and  authoritative  accounts  that  it  is  unnecessary 
to  deal  exhaustively  with  these  matters  here.  It  seems 
desirable,  however,  for  the  sake  of  clearness,  to  refer 
briefly  to  some  of  the  features  of  construction  and  operation 
which  bore  directly  upon  the  condition  of  the  air  at  the 
time  of  the  investigation. 


THE  AIR  OF  THE  NEW   YORK   SUBWAY  103 

Steel  and  concrete  in  the  subway.  The  subway  structure 
may  be  described  as  virtually  a  steel  cage  enclosed  and 
imbedded  in  concrete.  The  walls  and  roof  were  alike  in 
design.  They  found  their  strength  in  beams  weighing 
from  42  to  70  pounds  per  foot,  located  about  5  feet  apart. 
Between  these  beams  square,  steel  rods  1}  inches  were 
placed  to  the  extent  of  from  4  to  7  per  5-foot  panel.  Round 
rods  of  steel  f  inch  in  diameter  connected  the  columns 
about  2  feet  below  the  under  face  of  the  roof.  The  rods 
were  set  back  from  the  inner  face  of  the  tunnel  2  inches, 
but  the  beams  projected  to  the  surface. 

Between  the  beams  of  the  roof  and  sides  comparatively 
thin  walls  of  concrete  imbedded  the  steel  cage.  This 
concrete  has  a  thickness  at  the  walls  of  from  14  to  16 
inches,  exclusive  of  a  thin  protective  wall  of  water- 
proofing outside,  and  of  a  space  of  variable  thickness 
occupied  by  hollow  ducts  intended  to  contain  electric 
cables.  The  roof  has  a  thickness  which  varies  from  18J  to 
21 J  inches. 

In  the  four-track  section  of  the  subway  especially  studied 
in  this  investigation,  rows  of  steel  columns  extend  between 
each  two  lines  of  tracks  at  intervals  of  5  feet  to  support 
the  roof.  (See  Fig.  12.) 

The  floor  is  of  concrete  with  an  enclosed  layer  of  water- 
proofing. 

A  report  of  the  chief  engineer  of  the  Rapid  Transit 
Commission  supplies  data  from  which  the  amount  of 
masonry,  steel  and  water-proofing  can  be  calculated.1 

Stated  in  round  figures  the  quantities  of  material  handled 
in  building  the  subway  were  as  follows: 

1  Report  of  Wm.  Barclay  Parsons,  Chief  Engineer,  in  the  Annual 
Report  of  the  Board  of  Rapid  Transit  Commissioners  for  1904,  pp. 
246-251. 


104        THE  AIR  AND   VENTILATION  OF   SUBWAYS 


Brooklyn 
Bridge  to 

50th  St.  to 
96th  St. 

50th  St. 

Concrete  and  brick  per  mile  > 

cu.  yds.1 
tons  2 

46,000 
93,150 

44,000 
89,100 

Steel,  including  track    .... 

.    .      tons 

5,300 

5,400 

Waterproofing  
Material  excavated  — 

.   sq.  yds. 

82,000 

124,000 

Earth  . 

per  cent 

76 

52 

Rock 

per  cent 

24 

48 

Part  of  subway  in  operation.  The  part  of  the  road  which 
was  in  operation  during  the  period  of  this  investigation 
extended  from  the  lower  end  of  Manhattan  Island  north- 
ward to  96th  Street  and  Broadway,  where  it  divided,  one 
branch  continuing  along  Broadway  to  157th  Street,  and 
the  other  eastward  and  northward  until  it  crossed  under 
the  Harlem  River  and  reached  that  part  of  the  city  known 
as  the  Bronx. 

Nearly  all  of  this  road  was  underground.  There  was  a 
short  exposed  portion  of  a  few  blocks  covering  a  valley  at 
125th  Street,  and  the  branch  to  the  Bronx,  after  crossing 
the  Harlem,  soon  emerged  upon  an  elevated  structure, 
which  it  did  not  leave  to  the  end  of  the  line;  but  the  parts 
of  the  subway  which  were  not  underground  were  not  con- 
sidered in  this  investigation. 

Section  chosen  for  closest  observation.  The  considerable 
length  of  the  road,  about  21  miles,  and  the  rather  wide 
variety  of  conditions  which  occurred  in  it  made  it  desirable 
to  confine  the  investigation  as  far  as  practicable  to  a  rep- 
resentative section. 


1  At  1  cubic  foot  equals  150  pounds. 

2  At  1  ton  equals  2000  pounds. 


THE  AIR  OF  THE  NEW   YORK   SUBWAY 


105 


106        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

There  was  no  difficulty  in  selecting  this  section.  The 
road  between  96th  Street  and  the  Brooklyn  Bridge  was,  in 
every  respect,  the  most  important.  Further  on,  it  will  be 
shown  that  this  section  was  divisible  into  two  parts,  dis- 
tinct differences  both  as  to  details  of  construction  and  the 
condition  of  the  air  being  noticeable  between  the  part 
north  of  59th  Street  and  that  south. 

Nearly  all  the  studies  recorded  here,  except  those  of 
temperature  and  humidity,  refer  especially  to  the  repre- 
sentative section  between  96th  Street  and  the  bridge.  In 
many  cases,  however,  they  have  a  much  wider  application. 

The  length  of  the  section  was  about  6  miles.  The  cubic 
air  space  included  was,  in  round  figures,  26,100,000  cubic 
feet,  including  the  stations. 

The  section  was  four  tracks  wide,  excepting  a  piece  of 
tunnel  which  ran  between  42nd  Street  and  34th  Street. 
Here  there  were  two  tunnels  of  two  tracks  each,  running 
side  by  side,  cut  through  the  rock. 

Nature  of  the  travel.  The  nature  of  the  travel  in  the 
subway  was  largely  controlled  by  the  route  followed. 
Beginning  at  the  Battery,  at  the  southern  end  of  Manhattan 
Island,  the  line  first  passes  through  a  section  devoted 
exclusively  to  business.  This  district  is  highly  congested 
and  extends  to  the  Brooklyn  Bridge.  Practically  all  of  the 
passengers  who  entered  the  subway  below  the  Bridge  did 
so  with  the  intention  of  going  north. 

From  the  Brooklyn  Bridge  to  14th  Street,  the  subway 
runs  through  a  business  district  consisting  largely  of  whole- 
sale mercantile  and  light-manufacturing  establishments. 
Here  also  a  large  proportion  of  the  passengers  who  entered 
the  subway  were  bound  north. 

From  14th  Street  to  Times  Square  the  city  is  given  over 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  107 

chiefly  to  retail  shops,  theatres  and  large  transient  hotels. 
At  34th  and  42nd  Streets,  the  road  is  tributary  to  termini 
of  two  important  steam  railway  systems.  The  travel  in 
this  section  is  heavy  in  each  direction. 

From  Times  Square  to  96th  Street,  the  district  tributary 
to  the  subway  is  almost  exclusively  residential  in  character. 
Inasmuch  as  there  is  little  to  attract  persons  in  this  section 
to  points  further  north,  most  of  the  passengers  who  enter 
the  subway  are  south-bound.  People  who  take  the  sub- 
way at  96th  Street  are  also  usually  south-bound. 

The  volume  of  travel  is  indicated  by  the  official  state- 
ments of  the  tickets  sold  at  different  stations.1  These 
statements  do  not  mention  in  which  direction  the  pas- 
sengers were  going,  but  the  foregoing  information  con- 
cerning the  districts  traversed  gives  some  idea  of  these  facts. 

Taking  the  sales  of  tickets  at  different  stations  in  the 
month  of  September,  1905,  we  may  estimate  the  travel  as 
follows : 

Per  cent 

North-bound  from  Brooklyn  Bridge  and  south  ....  24.7 
Both  directions,  between  Brooklyn  Bridge  and  96th  St.  44 . 6 
South-bound,  from  96th  Street  and  north 30.7 

From  this  it  will  be  seen  that  many  more  people  entered 
the  subway  between  Brooklyn  Bridge  and  96th  Street  than 
passed  entirely  through  this  section  on  express  trains. 

If  we  divide  the  ticket  sales  in  a  more  detailed  way  and 
apply  the  same  reasoning  as  already  given  to  show  the 
direction  of  travel,  we  may  obtain  data  from  which  to 
construct  a  diagram  in  which  the  north  or  south  direction 
taken  by  the  passengers  is  shown  by  arrows,  and  the  com- 
parative number  of  travelers,  by  lines  of  different  height. 

1  Report  of  Board  of  Rapid  Transit  Commissioners  for  the  City  of 
New  York,  1905. 


108        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

Now,  if  the  figures  for  the  subway  fairly  represent  the 
average  conditions  which  occurred  during  the  period  from 
July  to  December,  1905,  inclusive,  we  have  a  ready  means 
from  which  to  estimate  the  numbers  of  passengers  carried 
in  each  direction  from  the  different  parts  of  the  subway 
during  this  investigation.  There  is  reason  for  believing 
that  these  conditions  were  fairly  representative. 

The  nature  of  the  business  done  by  the  subway  and  the 
distribution  through  the  line  indicates  to  some  extent  how 
the  amount  of  travel  varied  from  hour  to  hour.  Between 
the  hours  of  7  and  10  A.M.  and  4  and  7  P.M.,  the  capacity 
of  the  road  seemed  taxed  to  the  utmost.  It  is  probably 
very  close  to  the  facts  to  assume  that  over  one-half  of  the 
total  travel  for  the  day  was  carried  within  these  six  hours. 
Omitting  these  rush  periods,  there  was  probably  a  nearly 
constant  amount  of  travel  for  the  other  hours  of  the  day 
excepting  between  12  and  6  A.M.,  when  the  amount  of 
travel  was  inconsiderable  in  comparison  with  that  for  the 
other  hours. 

We  may,  therefore,  without  probability  of  serious  error 
assume  that  about  50  per  cent  of  the  passengers  carried 
each  day  was  accommodated  between  10  A.M.  and  4  P.M., 
and  7  P.M.  and  12  P.M. 

If  we  take  the  total  number  of  passengers  carried  on 
the  average  day  in  September,  1905,  to  have  been  295,000, 
as  shown  by  the  official  records  of  ticket  sales,  we  have 
about  25,000  per  hour  as  the  number  carried  in  the  rush 
hours  and  13,400  per  hour  during  the  other  hours  when  the 
travel  was  practically  at  a  standstill. 

In  the  autumn  of  1905,  the  rush-hour  travel  was  accom- 
modated largely  by  the  express  service.  Probably  80  per 
cent  of  the  travel  passed  entirely  through  the  section 
between  the  Brooklyn  Bridge  and  96th  Street. 


THE  AIR  OF  THE  NEW   YORK   SUBWAY  109 

Sanitary  features  of  construction.  By  the  contract  we 
learn  that  it  was  intended,  when  the  road  was  designed, 
that  it  should  be  easily  accessible,  light,  dry,  clean,  and 
well  ventilated. 

It  was  partly  to  accomplish  these  ends  that  the  road  was 
built  as  close  to  the  surface  of  the  streets  as  physical  con- 
ditions permitted. 

Dryness.  Much  care  was  taken  to  make  the  subway  dry. 
It  was  declared  to  be  the  "  very  essence  of  the  specifica- 
tions "  for  construction  to  secure  a  structure  which  would 
be  entirely  free  from  the  inward  percolation  of  ground,  or 
outside,  water. 

To  accomplish  this  end,  a  practically  continuous  sheet 
of  asphalt  was  built  within  the  concrete  bottom,  sides  and 
top  of  the  structure.  This  water-tight  envelope  consisted 
of  from  two  to  six  thicknesses  of  asbestos,  or  other  similar 
felt,  laid  in  hot,  natural  asphalt.  In  addition,  every  part 
of  the  road  was  so  drained  that  water  finding  access  thereto 
was  led  away  by  natural  drainage  or  automatic  pumps  to 
the  city  sewers. 

Lighting.  The  roof  of  the  subway  was  so  close  to  the 
level  of  the  streets  that  it  was  possible  for  the  builders  to 
make  extensive  use  of  vault  lights  for  illuminating  the 
stations  with  natural  light.  Full  advantage  was  taken  of 
the  possibilities  in  this  direction.  The  lights  were  made 
of  cast-iron  frames,  with  lenses  about  2J  inches  in  diameter 
of  strong  glass  set  in  cement.  The  area  of  the  vault  lights 
at  some  stations  was  so  great  that  little  artificial  light 
was  employed,  excepting  at  night.  Some  idea  of  the 
extent  to  which  these  vault  lights  were  used  can  be 
gained  from  the  fact  that  there  were  over  6000  square 
feet  at  Brooklyn  Bridge  and  over  5000  at  the  96th  Street 
station. 


110        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

Incandescent  lamps  were  the  only  artificial  lights  used 
except  for  signals. 

Provisions  for  cleanliness.  In  constructing  the  road, 
provisions  for  keeping  the  subway  clean  were  carefully 
carried  out  at  the  stations.  The  platforms  were  made  of 
cement  and  the  walls  of  tile,  the  joints  and  moldings  being 
such  as  to  permit  of  easy  cleaning.  The  stairways  were 
provided  with  safety  treads,  and  these  collected  much 
street  dirt,  thus  keeping  it  from  entering  the  subway. 

Provision  was  made  in  the  original  design  for  a  concrete 
roadbed,  which  would  have  enabled  the  road  to  be  kept 
clean  between  stations;  but  modifications  in  the  contract, 
after  it  was  let,  resulted  in  the  construction  of  a  broken 
stone  roadbed,  from  which  only  comparatively  large  par- 
ticles of  refuse  could  be  removed.  Smaller  particles  settled 
into  the  voids  and  finally  filled  them  so  that  at  many  places, 
particularly  at  stations,  the  roadbed  appeared  to  be  per- 
fectly smooth  and  black.  The  wooden  cross-ties  quickly 
became  saturated  with  the  oil  which  dripped  from  the 
machinery  of  the  motor  cars. 

Stations.  There  were  twenty  stations  on  the  section 
chosen  for  especially  careful  study.  Five  of  these  were 
for  express  and  the  remainder  for  local  purposes  only.  The 
express  stations  were,  on  an  average,  1 J  miles  apart  and  the 
local  stations  J  mile  apart. 

The  express  stations  have  two  large  island  platforms 
situated  between  the  express  and  local  tracks.  At  the 
Brooklyn  Bridge,  Grand  Central  and  14th  Street  stations, 
these  platforms  are  reached  by  overhead  bridges  above  the 
tracks,  but  underneath  the  street  surface.  The  island 
platforms  at  72d  Street  are  approached  by  stairways 
which  descend  from  a  more  or  less  ornamental  building 
located  in  the  center  of  the  Boulevard.  The  platforms  of 


THE   AIR   OF   THE   NEW   YORK  SUBWAY  11] 

the  96th  Street  station  are  reached  by  a  passageway 
running  beneath  the  tracks.  The  island  platforms  give 
access  to  either  local  or  express  trains  and  permit  passengers 
to  transfer  from  one  to  another. 

At  the  Bridge,  14th  Street  and  96th  Street,  side  plat- 
forms exist  in  addition  to  the  island  platforms,  but,  except- 
ing at  96th  Street,  they  were  not  used  at  the  time  of  this 
investigation. 

The  platforms  of  the  local  stations  are  about  200  feet 
long,  while  the  platforms  of  the  express  stations  are  about 
350  feet. 

The  local  stations  have  separate  platforms  from  which 
passengers  enter  or  leave  the  north-  or  south-bound  trains 
respectively.  These  platforms  are  located  outside  of  the 
roadway.  There  is  usually  no  provision  for  crossing  from 
one  platform  to  the  other.  At  two  local  stations,  however, 
Astor  Place  and  Times  Square,  passageways  are  con- 
structed under  the  railway. 

There  are  several  types  of  local  stations.  South  of  50th 
Street  there  are  two  platforms,  one  on  each  side  of  the 
street  and  outside  of  the  tracks.  They  are  as  wide  as  the 
width  of  the  street  permits.  They  extend  from  the  tracks 
to  within  5  feet  of  the  building  line.  As  far  as  practicable 
the  two  platforms  are  in  duplicate  and  extend  under  the 
cross  streets,  sufficient  street  being  excavated  to  make 
room  for  the  ticket  offices,  toilet  rooms  and  closets  which 
are  used  for  various  purposes. 

With  few  exceptions,  each  side  of  each  station  was 
equipped  with  two  sets  of  water-closets  for  the  use  of 
women  and  men,  respectively.  They  were  well  furnished 
with  bowl  hand  basins,  and  sinks,  each  of  which  was  sup- 
plied with  a  back-aired  trap  and  connected  with  a  sewer. 

The  closets  were  designed  to  be  ventilated  through  ducts 


112         THE   AIR  AND   VENTILATION   OF   SUBWAYS 

connected  with  the  street  above,  and,  toward  the  close  of 
this  investigation,  electric  exhaust  fans  were  set  in  many 
of  the  ducts  to  force  the  air  of  the  closets  into  the  street. 
At  the  beginning  of  this  investigation,  ventilation  was 
affected  only  through  the  doors  communicating  with  the 
subway. 

The  plans  of  four  types  of  subway  stations  showing  the 
stairway  openings  to  the  street  are  shown  in  Fig.  13. 


CANAL  ST.  STATION  .  96TH  ST.  STATION 

FIG.  13.     Plans  of  four  types  of  subway  stations.     Stairways  and  kiosk 
openings  shown  as  black  squares. 

Track.  The  track  consisted  of  a  standard  gauge  road- 
way, with  the  wooden  cross-ties  and  broken  stone  ballast, 
which  is  commonly  seen  on  the  best  steam  railroads  out  of 
doors.  This  type  was  adopted  at  the  request  of  the  operat- 
ing company,  after  the  general  contract  for  the  road  had 
been  let. 

The  original  contract  had  specified  that  in  the  under- 
ground portions  of  the  railway  the  tracks  should  consist 


THE   AIR  OF  THE  NEW  YORK   SUBWAY  113 

of  rails  laid  on  a  continuous  bearing  of  wooden  blocks,  the 
grain  of  which  was  to  be  transverse  to  the  length  of  the 
rail.  The  blocks  were  to  be  held  in  place  by  guard  rails 
secured  to  metal  cross-ties  imbedded  in  the  concrete  floor. 

Provisions  for  ventilation.  The  subway  was  ventilated 
through  the  stairways  at  the  stations  and  through  blow- 
holes in  the  roof. 

Blow-holes.  All  of  the  blow-holes  which  were  originally 
built  were  located  in  that  portion  of  the  road  which  lay 
above  60th  Street.  They  were  rectangular  in  shape,  and 
opened  upon  small  grass  plots  which  occupied  the  center 
of  the  wide  boulevard  known  as  Upper  Broadway.  Iron 
railings  surrounded  the  openings.  To  prevent  the  entrance 
of  large  objects,  the  openings  were  covered  with  coarse 
wire  netting. 

The  blow-holes  were  located  above  the  center  of  the 
railway,  one  being  situated  a  little  beyond  each  end  of  each 
station.  An  additional  blow-hole  was  placed  midway 
between  stations.  The  total  number  of  blow-holes  between 
59th  and  96th  Streets  was  eighteen.  Each  was  about 
7  X  14J  feet  in  the  clear.  Wire  nettings,  beams,  and  other 
objects  took  up  about  one-quarter,  or  more,  of  this  space, 
so  that  the  total  effective  area  from  these  blow-holes  was 
about  1,368  square  feet.  Early  in  the  investigation  sections 
of  the  vault  lights  were  removed  from  the  stations  at  72d 
and  96th  Streets  and  left  unobstructed  by  nettings.  The 
area  removed  at  72d  Street  was  about  108  square  feet  and 
at  96th  Street  about  478  square  feet.  This  greatly  relieved 
the  unsatisfactory  condition  of  the  air  at  72d  Street, 
where  the  subway  entrances  had  been  covered  by  a  build- 
ing, and  at  96th  Street  where  the  roof  was  very  low  and 
the  extent  of  vault  lights  extraordinarily  great. 


114        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

Stairways.  The  stairways  between  the  streets  and  the 
stations  varied  somewhat  as  to  width  and  direction.  Below 
59th  Street  they  were  usually  placed  at  right  angles  to  the 
line  of  the  road;  above  59th  Street  they  were  parallel  to  the 
road.  There  were  usually  two  stairways,  each  in  cross 
section  about  5J  X  7J  feet,  to  each  local  station  above  59th 
Street,  and  eight  narrower  ones  to  the  other  local  stations. 


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^-* 

—•—Ratio  of  effective  area  of                             Difference  between  amount 
openings  to  cubic  contents                           of  carbon  dioxide  inside 
of  air-space                                                    and  outside  of  subway 

FIG.  14.  Relation  between  the  chemical  condition  of  the  air  in  the 
subway  and  the  ratio  of  the  effective  area  of  the  openings  to  the  cubic 
contents  of  the  air  space  at  different  stations. 

The  stairways  were  covered  with  ornamental  kiosks, 
which  stood  upon  the  sidewalks  near  the  curbs.  They  were 
without  doors.  The  kiosks  opened  north  and  south  above 
59th  Street;  below  59th  Street  they  usually  faced  east  and 
west. 

The  relation  between  the  chemical  condition  of  the  air 
in  the  subway  and  the  ratio  of  the  effective  area  of  the 
openings  to  the  cubic  contents  of  the  air  space  at  different 
stations  is  shown  in  Fig.  14. 


THE  AIR  OF  THE  NEW  YORK   SUBWAY  115 

Phenomena  of  ventilation.  Exchanges  of  air  between 
the  subway  and  streets  took  place  chiefly  by  reason  of  the 
movement  of  trains. 

Effects  of  train  movements.  The  subway  was  about  50 
feet  wide  and  18  feet  high  on  the  four-track  section  between 
Brooklyn  Bridge  and  96th  Street,  and  the  cross  section  of 
a  car  occupied  about  14  per  cent  of  this  section.  The 
trains  were  from  about  150  feet  to  408  feet  long. 

•  The  number  of  passengers  in  the  cars  varied  somewhat 
at  different  hours  of  the  day,  but  the  cars  were  usually 
crowded.  There  were  fifty-two  seats  in  each  car,  and 
when  the  aisles  and  platforms  were  filled  the  total  number 
of  passengers  per  car  ranged  from  about  115  to  140.  The 
densest  crowding  occurred  in  the  rush  hours  and  through- 
out the  length  of  that  portion  of  the  subway  which  was 
under  closest  observation. 

The  number  of  cars  per  train,  the  number  of  trains  per 
hour,  and  the  speed  varied  at  different  hours.  The  local 
trains  usually  consisted  of  five  cars,  and  ran  at  a  rate, 
exclusive  of  stops,  of  about  21  miles  per  hour.  The  express 
trains  generally  consisted  of  eight  cars,  and  ran  at  a  rate, 
exclusive  of  stops,  of  about  26  miles  per  hour. 

The  total  number  of  passengers  carried  in  the  subway, 
as  indicated  by  an  official  statement  of  the  ticket  sales, 
averaged,  for  the  last  two  months  of  1905,  440,000  per  day. 
There  were  about  twice  as  many  passengers  carried  in 
November  and  December  as  in  July  (see  Table  I). 

As  a  train  moved  through  the  subway,  air  was  forced 
ahead  of  it  and  air  followed  it.  As  a  rule,  a  general  current 
flowed  along  the  track  on  each  side  of  the  subway  in  the 
direction  of  the  train  movement,  and  these  currents  con- 
tinued even  when  no  train  was  within  hearing  distance. 
The  important  action  of  a  train  was  to  force  air  along  with 


116         THE   AIR  AND   VENTILATION   OF   SUBWAYS 


it,  but  where  stairways  or  blow-holes  occurred  and  offered 
lines  of  diminished  resistance,  the  air  rushed  out  through 
them  as  a  train  approached  and  rushed  in  as  the  train 
went  by. 

TABLE  I. 

SHOWING    THE    NUMBER    OF    PASSENGERS    CARRIED    IN    THE 
SUBWAY    FROM    JULY    TO    DECEMBER,   1905,  INCLUSIVE. 

(From  the  Report  of  the  Board  of  Rapid  Transit  Commissioners  for  1905.) 


Rush 

Number  of 
passengers. 

Total  per 
day. 

hours 
7-10  A.M. 

Night 
12-6  A.M. 

Average. 

4-7  P.M. 

July 

6  076  241 

196  000 

106  000 

8  000 

82  000 

August  .    . 

7,085,814 

229,000 

126,000 

9,000 

94,000 

September 

8,843,314 

295,000 

159,000 

12,000 

124,000 

October    . 

11,329,216 

365,000 

197,000 

15,000 

143,000 

November 

12,677,761 

423,000 

229,000 

17,000 

177,000 

December 

13,715,946 

442,000 

241,000 

18,000 

183,000 

The  difference  in  barometric  pressure  necessary  to  set 
up  these  air  currents  was  exceedingly  slight;  the  effect  of 
friction  against  the  walls  and  pillars  of  the  subway  and  the 
sides  of  the  stairways  considerable.  A  great  part  of  the 
force  with  which  the  air  currents  were  set  in  motion  was 
generally  used  up  in  eddies  about  the  trains. 

The  movement  of  the  air  depended  upon  the  speed  of  the 
nearest  train,  the  movement  of  other  trains  in  the  vicinity, 
the  size  and  location  of  the  neighboring  openings  to  the 
outside  air,  the  size  of  the  particular  cross  section  of  the 
subway  with  reference  to  the  sections  of  the  moving  trains, 
the  force  and  direction  of  the  wind  in  the  streets  with 
reference  to  the  position  of  the  stairways,  the  difference  in 
temperature  inside  and  outside  of  the  subway,  and  other 
conditions. 


THE  AIR  OF   THE  NEW  YORK  SUBWAY 


117 


The  chemical  analyses  of  air  which  were  made  gave  data 
from  which  the  frequency  with  which  the  air  was  renewed 
could  have  been  computed  had  the  number  of  passengers 
present  at  any  corresponding  time  and  part  of  the  subway 
been  known.  Accurate  information  on  this  subject  was 
not,  however,  available.  From  approximate  computations 
made  in  a  number  of  ways,  it  is  practically  certain  that 
the  air  was  renewed  at  least  as  often  as  once  every  half 

hour. 

TABLE  II 

RESULTS  OF  COLOGNE  EXPERIMENTS,  SHOWING  RATE  OF  PAS- 
SAGE OF   AIR    FROM    STATION    TO    STATION 


Points  of  observation. 

Distance 
traveled. 

Time 
consumed. 

Speed. 

Stations. 

Feet. 

Minutes 
and 
seconds. 

Miles  per 
hour. 

Worth  Street  to  Brooklyn  Bridge  .    . 
Worth  Street  to  Canal  Street  .... 
Worth  Street  to  Canal  Street  .... 
Spring  Street  to  Canal  Street  .... 
Spring  Street  to  Canal  Street  .... 
Spring  Street  to  Canal  Street  .... 
Spring  Street  to  Bleecker  Street     .    . 
Spring  Street  to  Bleecker  Street     .    . 

Average   

835 
910 
910 
1,540 
1,795 
1,795 
1,230 
1,230 

5:25 
1:15 
7:35 
5:30 
10:10 
12:20 
3:40 
5:25 

1.75 
8.27 
1.36 
3.18 
2.00 
1.66 
3.81 
2.58 

3  08 

Anemometer  observations.  Observations  with  anemo- 
meters were  made  at  a  number  of  stations  on-  several 
occasions.  As  a  result  of  seventy-nine  of  these  obser- 
vations, covering,  in  the  aggregate,  two  hours  and  thirty- 
five  minutes,  made  at  eight  stations,  it  was  calculated  that 
an  average  of  573,000  cubic  feet  of  air  had  moved  in  and 
out  of  one  stairway  per  hour.  This  was  at  the  rate  of 
9,550  cubic  feet  per  minute. 


118        THE  AIR  AND  VENTILATION  OF  SUBWAYS 

The  maximum  movement  of  air  observed  was  when 
63,000  cubic  feet  passed  in  at  one  station  in  one  minute 
through  a  single  stairway.  The  velocity  of  the  current  on 
this  occasion  was  16 J  miles  per  hour. 

Circulation  of  air  between  stations.  That  the  air  cir- 
culated freely  from  one  station  to  another  was  shown  by 
C02  analyses  (to  be  referred  to  later)  and  by  noting  the 
time  that  it  took  an  odor  to  pass  from  one  station  to 
another.  Cologne  of  a  highly  concentrated  grade,  and  in 
sufficient  quantity  to  produce  a  distinct  perfume  through- 
out the  air  of  a  station,  was  used  at  several  points  and  the 
odor  noted  up  and  down  the  line  with  the  help  of  assistants 
with  stop  watches.  Care  was  used  that  the  cologne  should 
not  be  transported  mechanically  by  coming  in  contact 
with  the  trains  in  liquid  form.  The  results  of  the  cologne 
experiments  are  given  in  Table  II,  and  of  C02  analyses  in 
Table  IV. 

As  a  result  of  eight  cologne  experiments,  it  was  found 
that  the  odor  was  carried  from  station  to  station  at  the 


FIG.  15.     Cologne  Vaporizer  used  to  determine  the  rate  of  circulation  of 
air  in  the  New  York  Subway. 

average  rate  of  271  feet  per  minute,  or  about  3.08  miles  per 
hour.  The  cologne  vaporizer  used  in  these  experiments  is 
shown  in  Fig.  15.  It  was  about  three  feet  long. 

Ventilation  of  the  subway  and  human   lungs   compared. 
The  ventilation  of  the  subway  bears  an  interesting  resem- 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  119 

blance  to  the  ventilation  of  the  human  lungs,  and  it  will 
help  to  understand  the  former  if  we  trace  some  of  the 
details  of  this  analogy. 

The  ventilation  of  both  the  subway  and  the  lungs  is  due 
to  currents  of  air  passing  inward  and  outward  as  a  result 
of  changes  of  pressure,  caused  chiefly  by  the  expansion  and 
contraction  of  the  enclosed  space. 

It  is  true  that  with  the  lungs  the  size  of  the  enclosed 
space  is  alternately  enlarged  and  reduced  through  the 
movement  of  its  walls,  while  in  the  subway  the  size  of  the 
enclosure  is  increased  and  diminished  through  what  is 
termed  the  piston  action  of  the  trains ;  but  in  other  respects 
the  similarity  is  close. 

In  the  normal  amount  of  air  which  passes  out  of  the 
subway  on  the  approach  of  a  local  train,  and  is  replaced  by 
an  indraught  of  fresh  air  as  the  train  draws  away,  we  have 
what  physiologists,  in  speaking  of  the  ventilation  of  the 
lungs,  call  the  "  tidal  air."  In  the  additional  quantity 
which  is  drawn  in  by  the  express  trains,  we  have  the 
"  complemental  air,"  and  in  the  excess  which  is  forced  out 
by  express  trains  the  "  reserve  or  supplemental  air." 

These  three,  the  tidal,  complemental,  and  supplemental, 
we  may  term  the  "  respiratory  or  ventilating  capacity  " 
of  the  subway. 

Finally,  there  is  an  amount  of  air  which  remains  in  the 
subway  and  is  not  immediately  forced  into  the  streets  by 
any  combination  of  local  and  express  trains;  this  we  may 
call  the  "  residual  air." 

This  terminology  is  appropriate  and  convenient  for 
general  purposes,  and  it  would  be  well  if  it  should  come 
into  use  among  ventilating  and  sanitary  experts  in  dealing 
with  ventilation  problems  of  much  less  strictly  physiological 
character  than  those  to  which  it  has  hitherto  been  confined. 


120        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

Changes  in  the  ventilating  arrangements  of  the  New  York 
subway.  With  the  object  of  reducing  the  heat  which  had 
made  the  air  uncomfortably  warm  during  the  summer 
months,  extensive  alterations  were  made  in  the  ventilating 
arrangements  of  the  New  York  subway  in  1906-7  after  the 
investigations  covered  in  this  volume  were  completed. 
The  plan  embodied  several  features. 

Large  sections  of  the  roof  were  removed  at  the  stations 
and  the  openings  were  covered  with  gratings.  The  aggre- 
gate area  of  the  opening,  when  allowance  was  made  for  the 
gratings,  was  2,356  square  feet  in  the  section  from  the 
Brooklyn  Bridge  to  Columbus  Circle,  and  1 ,805  square  feet 
in  the  section  between  the  latter  point  and  96th  Street. 
It  was  calculated  by  the  engineers  of  the  Rapid  Transit 
Commission  that  these  openings,  together  with  the  open- 
ings at  the  station  stairways,  etc.,  would  give  a  ratio  of 
1  square  foot  of  blow-holes  for  every  3,200  cubic  feet  of 
contents  at  each  station. 

Blow-holes,  opening  generally  from  specially  constructed 
chambers,  were  also  provided  between  stations.  These 
blow-holes  were  fitted  with  air  valves  and  fans,  the  object 
of  the  arrangement  being  to  induce  fresh  air  to  enter  at 
the  stations  and  pass  out  through  the  blow-holes  between 
stations. 

The  air  valves,  called  louvres,  were  made  of  galvanized 
iron  and  were  so  fitted  into  sheet-iron  boxes  that  when 
shut  they  entirely  closed  the  area  of  the  blow-holes  in 
which  they  were  placed.  The  valves  swung  automatically 
upon  axles,  being  so  counterweighted  as  to  open  and  let 
out  air  when  it  was  forced  ahead  by  the  trains  and  then 
close  and  prevent  any  fresh  air  from  getting  in  after  the 
trains  had  passed. 

The  ventilation  with  the  valves  was  like  the  natural 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  121 

ventilation  which  would  have  taken  place  without  them, 
in  one  respect:  they  were  entirely  dependent  upon  the 
movements  of  the  trains,  producing  an  amount  of  venti- 
lation which  was  proportional  to  the  number  of  trains 
passing  in  a  given  period. 

Mr.  George  S.  Rice,  Chief  Engineer  of  the  Rapid  Transit 
Railroad  Commission,  has  fully  described  these  louvres  in 
his  report  to  the  Commission  for  1906.  He  states  that  a 
discharge  of  19,000  cubic  feet  of  air  has  been  observed  to 
take  place  through  100  square  feet  of  louvres  between  6 
A.M.  and  8  P.M.,  an  average  of  14,400  cubic  feet  between 
8  P.M.  and  1  A.M.  and  4,800  cubic  feet  between  1  A.M. 
and  6  P.M.  under  conditions  of  average  working. 

The  louvre  openings  between  Brooklyn  Bridge  and 
Columbus  Circle  were  estimated  by  Mr.  Rice  to  have  a 
capacity  of  passing  675,000  cubic  feet  of  air  per  minute 
which,  being  replaced  by  fresh  air  coming  in  through  the 
stations,  is  equivalent  to  a  renewal  of  all  the  air  of  this 
section  about  once  in  27  minutes.  Similarly  the  valves 
between  Columbus  Circle  and  96th  Street  were  considered 
to  be  capable  of  renewing  the  air  in  this  section  about 
once  in  33  minutes. 

The  fans  have  been  placed  at  the  ventilating  openings 
between  stations  to  accelerate  ventilation  under  special 
circumstances,  such,  for  example,  as  at  night  when  few 
trains  are  running  and  in  order  to  free  the  subway  of  smoke 
in  case  of  fire.  The  fans  are  of  the  centrifugal  type  pop- 
ularly known  as  blowers.  They  are  from  5  to  7  feet  in 
diameter.  They  are  operated  by  electric  motors  of  15  to 
30  horse  power  capacity,  and  when  run  at  their  normal 
speed  of  235  to  330  revolutions  per  minute  are  said  to  be 
capable  of  discharging  about  990,000  cubic  feet  of  air  per 
minute.  On  the  basis  that  the  fans  are  really  capable  of 


122        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

operating  as  effectively  as  assumed,  they  should  be  able 
to  renew  the  air  in  the  section  between  Columbus  Circle 
and  Brooklyn  Bridge  in  nineteen  minutes. 

A  plant  for  cooling  the  air  at  the  Brooklyn  Bridge  station 
was  constructed  in  1906.  The  project  required  that  the 
heated  air  of  this  station  should  be  passed  by  means  of  a 
centrifugal  fan  over  coils  of  cold  water  and  distributed 
through  ducts  opening  immediately  over  the  heads  of  the 
passengers  at  stations.  The  plant  was  designed  by  Mr. 
John  E.  Starr  and  is  fully  described  in  the  report  of  Chief 
Engineer  Rice,  already  referred  to. 

The  water  for  the  cooling  plant  is  obtained  from  an  arte- 
sian well  from  which  the  report  says  it  is  pumped  at  the  rate 
of  about  200  gallons  per  minute.  The  quantity  of  air 
cooled  is  about  75,000  cubic  feet  per  minute  for  each  of  the 
two  units  into  which  the  plant  is  divided. 

The  cooling  arrangement  at  the  Brooklyn  Bridge  was 
put  in  operation  August  29,  1906,  and  has  been  run  inter- 
mittently during  the  hot  weather.  When  first  put  in 
operation,  it  was  found  that  there  was  a  transfer  of  heat 
between  9.4  and  11.3  B.  T.  U.  per  square  foot  per 
degree  of  difference  between  the  air  and  the  water,  and 
that  the  air  which  came  in  contact  with  the  pipes  could 
be  cooled  about  8  degrees  under  the  conditions  of  practical 
operation. 

The  flow  of  air  from  the  openings  in  the  ducts  over  the 
platforms  was  perceptible  for  a  distance  of  5  or  6  feet  below 
the  center  of  the  openings.  Although  the  regular  pas- 
sengers at  this  station  took  up  positions  immediately  under 
the  openings  when  the  plant  was  operated,  the  effect  seems 
not  to  have  been  perceptible  to  the  senses  at  other  points 
in  the  stations. 

Practically  none  of  the  changes  in  ventilation  were 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  123 

completed  before  the  investigations  described  in  this 
volume  were  finished,  although  experiments  with  fans  and 
blow-holes  were  being  made  toward  the  conclusion  of  the 
investigating  work. 

TEMPERATURE   AND    HUMIDITY 

From  an  early  period  in  the  construction  of  the  road,  an 
effort  had  been  made  to  observe  the  temperature  and 
humidity  at  a  number  of  points  by  means  of  automatic, 
recording  thermometers.  Later,  when  the  sanitary  con- 
ditions were  being  made  the  subject  of  investigation,  these 
records  were  critically  examined  and  the  observations  put 
upon  a  more  exact  basis. 

In  this  section  we  will  briefly  review  the  early  and  later 
methods  and  the  final  system  of  observing  temperatures, 
and  then  pass  to  a  consideration  of  the  results  of  all  obser- 
vations. 

Methods  employed.  The  various  methods  employed 
may  conveniently  be  considered  separately. 

Early  metfwds.  The  earliest  date  upon  which  any 
systematic  record  of  temperature  or  humidity  was  made 
in  the  subway  was  June  26,  1903.  At  that  time  a  number 
of  maximum  and  minimum  thermometers  and  stationary 
wet  and  dry  bulb  hygrometers,  with  some  small  Richard 
thermographs,  were  placed  in  the  subway  at  various 
places  between  the  City  Hall  and  Columbus  Circle  stations, 
at  different  points  on  the  line  above  50th  Street,  and 
outside. 

The  accuracy  of  the  observations  made  with  these 
instruments  was  carefully  studied  by  the  author  in  July, 
1905.  The  temperature  records  were  found  to  be  generally 
accurate,  probably  to  within  5  degrees,  and  the  humidity 


124        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

observations  to  within  20  per  cent.  The  readings  were  all 
generally  too  high. 

Methods  used  from  July  1  to  September  18,  1905.  After 
the  work  of  observing  temperatures  and  humidities  came 
under  the  author's  direction,  no  maximum  and  minimum 
thermometers  nor  stationary  wet  and  dry  bulb  hygro- 
meters were  employed. 

Temperature  and  humidity  observations  were  first 
undertaken  in  this  investigation  on  July  1,  1905.  They 
were  made  with  sling  psychrometers  designed  as  made  for 
the  United  States  Weather  Bureau,  with  some  minor 
changes  intended  to  fit  them  especially  for  subway  work. 

The  psychrometers  consisted  of  two  mercurial  ther- 
mometers 24  centimeters  long,  graduated  from  —  10  to  125 
degrees  Fahrenheit,  fastened  upon  an  aluminum  back, 
1J  centimeters  apart,  center  to  center.  (See  Fig.  16.) 

The  bulbs  projected  beyond  the  aluminum  back  for 
about  5  centimeters,  one  of  the  bulbs  being  covered  with 
cotton  cloth.  The  upper  end  of  the  aluminum  back  was 
connected  by  two  loose  wire  links,  fitted  by  a  pivot  to  a 
substantial  handle  around  which  the  thermometers  could 
be  whirled. 

To  make  it  conveniently  transportable,  the  whole 
instrument  was  fitted  into  a  specially  designed  cylindrical 
aluminum  case,  and  was  there  secured  by  a  bayonet  lock 
at  the  top.  The  case  was  arranged  so  as  to  hang  from  a 
leather  strap,  so  that  the  instrument  might  be  slung  over 
the  shoulder  when  not  in  use.  The  psychrometers  were 
made  by  Schneider  Brothers,  265  Green  Street,  New 
York. 

The  manner  in  which  the  sling  psychrometer  was 
employed  and  the  tables  used  to  calculate  the  humidity 
from  the  readings  are  contained  in  W.  B.  No.  235,  issued 


125 


126         THE   AIR  AND   VENTILATION   OF   SUBWAYS 

by  the  Weather  Bureau  of  the  United  States  Department 
of  Agriculture. 

When  tested  at  a  testing  station,  established  for  the 
purpose  of  determining  the  accuracy  of  the  various  instru- 
ments employed  in  the  investigation,  the  thermometers 
were  found  to  be  accurate  to  within  one-tenth  of  1  degree 
Fahrenheit. 

Four  observers  were  regularly  employed  in  making  the 
psychrometer  observations.  Each  visited  a  given  number 
of  stations  per  day,  between  9  A.M.  and  5  P.M.,  and  recorded 
the  temperature  and  humidity  inside  and  outside  of  the 
subway.  The  express  stations  were  visited  twice. 

In  making  an  observation  at  a  station,  the  observer  took 
into  account  the  air  throughout  the  entire  length  of  the 
platform.  It  was  usual  to  make  five  observations  at 
about  equal  distances  from  one  end  of  a  platform  to  the 
other.  Each  observation  consisted  of  at  least  four  readings 
of  the  thermometers.  The  readings  were  recorded  in 
notebooks  to  the  nearest  half  degree. 

At  first  sight  it  may  appear  that  these  data,  obtained  at 
only  certain  hours  of  the  day,  with  the  late  afternoon  and 
early  morning  left  out,  may  give  a  misleading  idea  of  the 
average  temperatures  for  the  twenty-four  hours.  This, 
however,  is  not  the  fact.  Continuous  observations  carried 
on  day  and  night  for  a  week  showed  that  the  data  so 
obtained,  when  worked  into  averages  for  days  and  weeks, 
gave  an  excellent  knowledge  of  the  conditions. 

The  total  number  of  temperature  and  humidity  observa- 
tions to  November  16  was  about  50,000,  considering  the 
temperature  and  humidity  observations  separately. 

Final  system  of  observing  temperatures.  The  observa- 
tions with  sling  psychrometers  were  not  intended  to  furnish 
the  data  from  which  the  most  important  deductions  con- 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  127 

earning  the  temperature  were  to  be  derived.  The  instru- 
ments selected  for  this  purpose  were  thermographs. 

The  suitability  of  practically  every  well-known  ther- 
mograph on  the  market  was  considered  for  this  use. 
Specimens  of  five  makes  were  set  up  in  the  testing  station 
and  compared  for  several  weeks  before  a  choice  was  finally 
made.  ' 

The  instruments  chosen  were  the  largest  thermographs 
made  by  J.  Richard,  Paris.  About  one  dozen  of  these  were 
especially  imported  for  subway  use;  others  were  obtained 


FIG.  17.     A  Richard  Thermograph. 

in  America.  The  total  number  of  thermographs  which 
were  put  in  use  was  twenty.  On  test  they  were  found  to 
be  capable,  under  the  practical  conditions  required,  of 
recording  changes  of  temperature  to  within  one  degree  and 
time  to  within  ten  minutes,  if  visited  daily  and  kept  clean 
and  adjusted. 

As  may  be  supposed,  the  thermographs  never  showed 
the  changes  of  temperature  which  actually  occurred.    They 


128        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

were  most  accurate  when  the  changes  were  slow  and  not 
very  decided.  To  be  precise,  the  thermograph  curves 
could  be  interpreted  as  neither  more  nor  less  than  the 
record  of  the  net  effect  of  several  conditions,  only  the 
leading  one  of  which  was  the  temperature  of  the  subway 
near  the  instrument. 

Observations  with  a  delicate  mercurial  thermometer 
showed  that  changes  of  temperature  occurred  in  the 
subway  of  far  greater  extent  and  frequency  than  were 
indicated  by  the  thermographs.  (See  Figure  4.)  But  if 
they  did  not  give  a  scientifically  perfect  record  of  every 
change  of  temperature,  they  were  none  the  less  serviceable. 
It  was  not  desired  to  know  each  change,  but  only  the  more 
decided  and  lasting  ones. 

A  special  observer  was  trained  to  keep  the  thermographs 
in  good  condition,  to  check  their  readings  with  an  accu- 
rate mercurial  thermometer,  to  make  necessary  adjust- 
ments, to  wind  the  clocks,  and  to  renew  the  record  sheets 
every  week.  The  records  were  systematically  filed.  (See 
Figure  17.) 

The  management  of  the  thermographs  and  the  observa- 
tions of  relative  humidity  were  turned  over  to  the  engineer- 
ing corps  of  the  board  on  November  18,  with  the  recom- 
mendation that  the  system  be  made  permanent. 

The  thermographs  were  placed  in  specially  constructed 
cages  in  the  stations  of  the  subway,  generally  at  the  end  of 
the  platform  which  was  approached  by  incoming  trains. 
They  were  as  far  removed  as  possible  from  local  draughts, 
and  about  4  feet  above  the  pavement. 

The  thermographs  located  out  of  doors  were  placed  in 
cages  of  similar  construction  to  those  used  underground. 
The  locations  of  the  outside  thermographs  were  selected 
with  a  view  to  having  the  instruments  in  the  shade,  remote 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  129 

from  the  effects  of  radiation  from  pavements  and  buildings, 
and  beyond  the  influence  of  outrushing  currents  of  air  from 
the  subway. 

The  records  obtained  from  the  thermographs  gave  an 
excellent  idea  of  the  average  differences  in  temperature 
which  existed  between  the  subway  and  streets  and  between 
one  subway  station  and  another.  They  also  showed 
fluctuations  in  temperature  which  gave  clews  to  the  origin 
of  the  heat,  to  the  extent  and  ways  in  which  ventilation 
took  place,  to  the  movements  of  trains,  and  many  other 
instructive  matters. 

Throughout  the  period  of  this  investigation,  observa- 
tions of  temperature  Were  made  by  the  company  which 
operates  the  subway.  These  observations  consisted  of 
hourly  readings  of  ordinary  tin-backed  thermometers 
inside  and  outside  of  the  stations.  The  thermometers  were 
usually  read  by  colored  porters,  few  of  whom  were  com- 
petent to  do  this  work  properly.  None  of  these  records  is 
used  in  this  paper. 

Results    of    temperature   and  humidity  observations. — 

Before  the  subway  was  opened  for  travel.  In  view  of  the 
overheating  of  the  subway,  which  has  been  a  character- 
istic of  the  road  since  1905,  it  is  interesting  to  review 
some  of  the  temperature  characteristics  of  the  road  before 
it  was  thrown  open  to  travel.  In  reviewing  these  figures, 
it  must  be  remembered  that  the  entrances,  exits,  and 
blow-holes  were  more  or  less  closed  at  this  time,  and  that 
a  free  circulation  of  air  in  and  out  was  correspondingly 
obstructed.  Had  all  the  openings  been  free,  there  would 
have  been  less  difference  between  the  inside  and  outside 
air. 

During  construction,  and  before  the  subway  was  covered 


130        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

by  a  roof,  its  temperature  was  practically  that  of  the 
outside  air. 

After  the  roof  was  put  on,  marked  differences  occurred. 
The  temperature  of  the  subway  was  now  much  more  con- 
stant than  that  outside. 

Before  trains  were  run,  hourly  and  daily  changes  of 
temperature  in  the  streets  seemed  to  affect  the  subway  but 
little.  The  more  marked  and  continued  changes,  however, 
produced  visible  effects. 

In  winter  the  air  outside  was  cooler,  and  in  summer 
warmer,  than  the  air  of  the  subway.  The  total  range  of 
temperature  of  the  subway  air  at  112th  Street  for  the  year, 
August  6,  1903,  to  July  27, 1904,  was  from  22  to  68  degrees, 
or  46  degrees;  while  the  range  outside  was  from  2  to  94 
degrees,  or  92  degrees.  In  other  words,  the  range  of 
temperature  in  the  streets  was  twice  as  great  as  the  range 
in  the  subway. 

During  the  hottest  week  in  the  subway,  before  it  was 
opened,  the  temperature,  according  to  the  112th  Street 
records,  averaged  59.4  degrees,  while  the  street  temperature 
was  77.7  degrees.  At  its  hottest,  the  subway  was  18.3 
degrees  cooler  than  the  streets. 

The  early  records  of  temperatures  in  the  subway  give  no 
idea  of  the  normal  temperature  of  the  earth  through  which 
the  subway  runs.  The  temperature  probably  varies 
according  to  the  depth  under  the  surface,  the  presence  or 
absence  of  ground  water,  the  nature  of  the  rock  or  earth, 
and  other  conditions.  In  the  deep  tunnel  which  runs  under 
Central  Park,  a  temperature  of  54  degrees  was  frequently 
observed  in  June  and  July,  1903,  although  the  temperature 
outside  at  the  same  time  occasionally  reached  95  degrees. 

In  the  year  in  which  the  road  was  opened  for  travel,  the 
subway  at  Columbus  Circle  (59th  Street)  averaged  about 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  131 

53  degrees  warmer  than  the  average  temperature  in  the 
streets. 

In  March  and  April  the  average  temperatures  inside  and 
out  were  practically  the  same. 

From  the  middle  of  April  to  the  end  of  September,  the 
subway  at  Columbus  Circle  was  cooler  than  the  streets. 

Immediately  after  opening  the  subway  to  travel.  From 
the  middle  of  August  until  the  opening  day,  October  27, 
1904,  the  subway  was  gradually  cooling  from  the  highest 
point  which  it  had  reached  in  the  summer.  From  that 
time  to  the  end  of  the  year  the  temperature  gradually  fell. 

The  large  amount  of  travel  which  the  subway  experienced 
at  the  start  did  not  visibly  affect  the  decline  of  temperature 
which  was  to  be  expected  at  this  season  of  the  year. 

For  the  first  ten  weeks  of  1905,  the  subway  was  slightly 
warmer  than  in  1904.  It  is  not  clear  that  this  difference 
was  due  solely  to  the  fact  that  the  road  was  in  operation. 
The  temperature  out  of  doors  was  warmer  than  it  had  been 
the  year  before. 

Beginning  about  the  middle  of  March,  or  at  that  season 
when,  in  other  years,  the  temperature  inside  and  outside 
had  been  about  the  same,  the  heating  due  to  the  operation 
of  the  road  first  became  distinctly  visible.  Instead  of  the 
streets  becoming  warmer  than  the  subway,  as  had  been 
the  case  the  year  before,  the  temperature  inside  rose  also. 
Thenceforth  a  higher  temperature  in  the  subway  became 
the  rule,  both  winter  and  summer. 

The  summer  of  1905.  Throughout  the  investigation 
with  which  this  paper  is  concerned,  the  subway  was 
generally  warmer  than  the  streets.  The  only  exceptions 
were  when  the  outside  temperature  rose  rapidly  after  a 
prolonged  low  period.  This  usually  occurred  in  summer 
in  the  middle  of  the  day,  and  in  winter  after  a  cold  snap. 


132        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

The  excess  of  subway  temperature  over  outside  tem- 
perature increased  considerably  during  the  autumn  and 
winter  months.  In  the  early  part  of  July  the  difference 
between  the  temperature  for  the  whole  day  inside  and 
outside  of  the  subway  was  less  than  5  degrees.  In  the 
latter  part  of  September  it  was  over  10  degrees.  In 
January,  it  was  at  some  stations  about  20  degrees.  An 
average  daily  difference,  for  a  week,  of  30  degrees  was  found 
at  one  station. 

Referring  now  to  the  observations  of  temperature  made 
with  the  dry  bulb  thermometers  of  the  sling  psychrometers, 
we  are  prepared  to  obtain  a  better  idea  of  the  conditions 
which  obtained  in  the  summer  after  the  subway  was 
opened. 

The  subway  grew  warmer  as  the  summer  advanced.  It 
averaged  81  degrees  through  July,  1905.  In  the  week  of 
August  4  to  10,  it  was  83.4  degrees.  Thereafter  it  declined 
very  gradually,  until  the  latter  part  of  September,  when 
it  was  76  degrees. 

In  the  week  of  September  29  to  October  5,  there  was  a 
slight  rise  to  78  degrees,  corresponding  with  a  rise  of  tem- 
perature out  of  doors.  This  was  followed  by  a  more  rapid 
decline  than  had  occurred  at  any  time  before.  Uncom- 
fortably high  temperatures  were  not  again  experienced  in 
1905. 

During  its  hottest  period  the  temperature  of  the  subway 
followed  the  temperature  of  the  outside  air,  except  in  the 
more  extreme  and  rapid  changes  of  the  latter.  This 
correspondence  is  seen  to  be  most  marked  when  the  data 
for  inside  and  outside  are  compared  in  the  form  of  weekly 
and  monthly  averages  (see  Table  III  and  Fig.  18). 

The  temperature  in  the  subway  for  the  daytime  for  July 
and  August,  combining  the  records  of  these  two  months  to 


THE  AIR  OF  THE  NEW   YORK  SUBWAY 


133 


form  an  average,  was  82.4  degrees;  it  was  76.8  degrees 
outside;  difference,  5.6  degrees. 

Highest  temperatures  in  the  summer  of  1905.     The  highest 
temperature  observed  in  the  subway  during  the  investi- 


AUG08T  SEPTEMBER  OCTOBER 

7        14        21       88  I     4         11        18       86      I  8         9         16        28 


AVERAG 


E  TEMPE 


RES 


\ 


FIG.  18.  Weekly  average  temperatures  in  the  subway  and  streets  from 
July  10  to  November  13,  1905.  These  averages  are  made  up  of 
47,476  observations. 

gation  was  95  degrees.  This  occurred  at  the  Brooklyn 
Bridge  station,  July  18,  1905,  at  3.50  P.M. 

The  hottest  week  was  that  of  August  4  to  10,  inclusive. 
The  average  daily  temperature  for  the  subway  during  this 
time  was  83.4  degrees;  for  the  outside  air,  78.2  degrees; 
difference,  5.2  degrees. 

The  maximum  temperature  observed  in  the  subway 
during  this  hottest  week  was  88.2  degrees;  in  the  streets 
it  was  88.2  degrees  at  the  same  time. 

The  warmest  and  coolest  stations.  The  coolest  station 
was  Canal  Street,  and  the  warmest  Astor  Place.  Synchro- 
nous curves  of  temperature  for  some  stations  and  the 
street  are  given  in  Fig.  19. 

The  lowest  temperature  recorded  at  Canal  Street  up  to 
January  1  was  30  degrees.  The  outside  temperature  at 


134        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

the  same  time  was  14  degrees,  giving  a  difference  of  16 
degrees.  At  the  same  time,  the  temperature  at  the  Brook- 
lyn Bridge  and  Astor  Place  stations  was  54  degrees.  Or, 


4 


Si 
•  ^ 


CO 


II 

GO      0) 


in  other  words,  the  Brooklyn  Bridge  station  was  40  degrees 
warmer  than  the  outside  air,  while  the  Canal  Street  station 
was  but  16  degrees  warmer. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


135 


The  express  stations,  with  the  exception  of  96th 
Street,  which  was  exceptionally  open  to  the  outside  at- 
mosphere, were  all  warmer  than  the  local  stations  in  their 
vicinity. 

The  coolest  stations  were  those  which  were  most  open 
to  the  street;  the  hottest  the  most  closed. 


PERCENT  OF  HUMIDITY 

S  S  §  3 

JULY 
0        17        24       8 

AUGUST                                    SEPTEMBER                                OCTOBER                     1      NOV. 
7        14       21      28   1    4         11        18       26     1  S         9        10        23      80  1        6        1 

/ 

// 

\ 

\ 

/ 

•  «** 

"«>« 

t 

\ 

^^ 

?**f 

\ 

—       •. 

/ 

/ 

«^\ 

/ 

4!£ 

J^v- 

/ 

\ 

/, 

^ 

~L 

\ 

u^ 

\ 

\ 

y 

\ 

/ 

X| 

i^ 

—  — 

\. 

FIG.  20.  Weekly  average  relative  humidity  in  the  subway  and  streets 
from  July  10  to  November  13,  1906.  These  averages  are  made  up  of 
47,456  observations. 


Humidity.  The  relative  humidity  in  the  subway  was 
generally  less  than  that  out  of  doors,  but  the  temperature 
of  the  dew  point  was  higher.  This  is  shown  in  Figs.  20 


S  ^ 
2 

Q 

!"! 

S    JU 

I 


1906 

JULY                                      AUGUST 

0        17       24       O        7         14       21       28 

SEPTEMBER                                    OCTOBER                    I       NOV. 
4          11        18        26     I   2         •          16       23       8Q         S          1 

V 

\\ 

/f 

x\ 

\ 

\ 

—-~-' 

/ 

s 

-~c 

**    — 

^4" 

/t 

\ 

\ 

z 

^ 

H*?V 

\    / 

\\ 

/ 

i 

'«\ 

f 

2 

77. 

\\ 

/ 

^& 

\ 

/ 

\ 

/* 

\\ 

L 

\ 

^ 

^ 

\ 

\ 

\    ' 

\ 

FIG.  21.     Weekly  average  temperature  of  the  dew  point  in  the  subway 
and  streets  from  July  10  to  November  13,  1906. 


136         THE   AIR  AND   VENTILATION   OF   SUBWAYS 


TABLE   III 

WEEKLY  AVERAGE,  MAXIMUM  AND  MINIMUM  TEMPERATURE,  AND 
RELATIVE  HUMIDITY  IN  THE  SUBWAY  AND  STREETS  AS  DE- 
TERMINED BY  SLING  PSYCHROMETER  OBSERVATIONS  FROM 
JULY  1  TO  NOVEMBER  16,  1905.  THE  NUMBER  OF  OBSERVA- 
TIONS INCLUDED  IN  THIS  TABLE  IS  97,168 


Date,  1905. 

Place. 

Average 

Maximum 

Minimum 

Temper- 
ature. 

Humid- 
ity. 

Temper- 
ature. 

Humid- 
ity. 

Temper- 
ature. 

Humid- 
ity. 

July  1-13 

Subway 
Surface 

83.3 
79.6 

61.5 
68.8 

90.0 
88.4 

95.0 
88.0 

74.0 
73.0 

30.0 
28.0 

Difference 

3.7 

7.3 

July  14-20 

Subway 
Surface 

83.2 
84.2 

51.6 

48.7 

95.0 
100.0 

69.0 
80.0 

72.0 
71.6 

36.0 
32.5 

Difference 

1.0 

2.9 

July  21-27 

Subway 
Surface 

82.4 
76.3 

50.7 
48.6 

90.6 
84.0 

85.0 
81.0 

70.0 
67.6 

31.5 
21.0 

Difference 

6.1 

2.1 

July  28-Aug.  2 

Subway 
Surface 

81.2 

74.7 

55.7 
59.6 

88.6 
85.0 

91.0 
86.0 

67.0 
62.8 

28.5 
32.0 

Difference 

6.5 

3.9 

Aug.  4-10 

Subway 
Surface 

83.4 
78.2 

64.4 
69.5 

88.  i 
88.2 

86.0 
93.0 

71.5 
70.0 

52.5 
31.0 

Difference 

5.2 

5.1 

Aug.  11-17 

Subway 
Surface 

81.5 
72.8 

59.0 
70.3 

89.0 
88.0 

85.0 
100.0 

69.5 
59.0 

34.0 
38.0 

Difference 

8.7 

11.3 

Aug.  18-24 

Subway 
Surface 

81.2 
76.9 

55.8 
59.5 

87.8 
90.0 

84.5 
83.0 

68.0 
65.0 

35.0 
34.5 

Difference 

4.3 

.7 

Aug.  25-31 

Subway 
Surface 

79.5 
72.0 

57.1 
62.7 

88.5 
81.9 

94.0 
100.0 

67.2 
63.0 

30.0 
33.5 

Difference 

7.5 

5.6 

Sept.  1-7 

Subway 
Surface 

79.3 
71.8 

54.5 
61.4 

85.0 
77.5 

84.0 
92.0 

70.0 
66.2 

38.0  ' 
39.0 

Difference 

7.5 

6.9 

THE  AIR  OF  THE  NEW  YORK  SUBWAY  137 

TABLE  III  —  Continued 


Date,  1905. 

Place. 

Average 

Maximum 

Minimum 

Temper- 
ature. 

Humid- 
ity. 

Temper- 
ature. 

Humid- 
ity. 

Temper- 
ature. 

Humid- 
ity. 

Sept.  8-14 

Subway 
Surface 

78.4 
66.5 

52.0 
59.0 

84.5 
79.5 

85.0 
88.5 

61.0 
52.8 

26.0 
21.5 

Difference 

11.9 

7.0 

Sept.  15-21 

Subway 
Surface 

78.1 
70.2 

62.2 
73.9 

84.2 
76.5 

89.0 
99.0 

63.2 
60.5 

33.5 
43.0 

Difference 

7.9 

11.7 

Sept.  22-28 

Subway 
Surface 

76.0 
66.0 

40.5 
45.0 

84.2 
81.2 

72.5 
74.2 

59.2 
47.8 

22.0 
28.0 

Difference 

10.0 

4.5 

Sept.  29-Oct.  5 

Subway 
Surface 

78.0 
72.1 

52.6 
57.7 

83.8 
81.8 

79.0 
91.0 

68.8 
64.1 

38.0 
33.0 

Difference 

5.9 

5.1 

Oct.  6-12 

Subway 
Surface 

74.4 
63.4 

42.6 
51.2 

82.2 
80.0 

62.0 
87.0 

59.0 
51.7 

24.0 
26.0 

Difference 

11.0 

8.6 

Oct.  13-19 

Subway 
Surface 

73.6 
63.0 

53.2 
61.6 

81.7 
76.8 

80.0 
93.0 

60.9 
45.8 

29.0 
31.5 

Difference 

10.6 

8.4 

Oct.  20-26 

Subway 
Surface 

Difference 

67.3 
53.7 

44.2 
59.5 

79.0 
69.1 

90.0 
98.5 

49.9 
42.2 

23.0 
28.0 

13.6 

15.3 

Oct.  27-Nov.  2 

Subway 
Surface 

Difference 

65.6 
49.4 

16.2 

42.3 
56.0 

74.1 
59.0 

76.5 
90.0 

48.8 
38.9 

21-0 
28.5 

13.7 

Nov.  3-9 

Subway 
Surface 

64.6 
50.1 

42.5 
58.9 

73.0 

58.5 

77.0 

88.0 

50.8 
41.5 

26.0 
33.0 

Difference 

14.5 

16.4 

Nov.  10-16 

Subway 
Surface 

60.8 
42.3 

34.6 
51.2 

71.0 
58.0 

63.0 
86.0 

41.8 
24.0 

15.0 

10.0 

Difference 

18.5 

16.6 

138        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

and  21.  In  other  words,  the  actual  weight  of  aqueous 
vapor  present  was  greater  in  the  subway  than  outside, 
but  it  appeared  to  be  less  in  the  subway  than  in  the 
streets. 

The  humidity  in  the  subway  varied  with  the  humidity 
out  of  doors. 

There  were  no  fogs  nor  mists  in  the  subway.  A  faint 
haze  was  not  uncommon. 

The  average  relative  humidity  for  the  subway  for  July 
and  August  was  57.5  per  cent;  for  the  outside  air,  60.6  per 
cent;  difference,  3.1  per  cent. 

The  greatest  average  relative  humidity  occurred  during 
the  week  when  the  average  temperature  was  highest. 
During  this  period  the  relative  humidity  averaged  64.4 
per  cent. 

Condensed  records  of  humidity  are  given  in  Table  III. 


CHAPTER  VI 

AIR  OF  THE  NEW  YORK  SUBWAY,   CONTINUED 
CHEMICAL  CONDITION  OF  THE  AIR 

THE  chemical  analyses  of  air  were  confined  chiefly  to 
determinations  of  carbon  dioxide,  for  it  was  thought  that 
no  other  test  could  give  such  a  correct  knowledge  of  the 
extent  to  which  the  air  was  vitiated  by  respiration,  and 
none  could  be  made  on  such  a  large  scale  as  was  wanted 
with  so  little  probability  of  error. 

Methods  of  analyses.  —  Analyses  for  carbon  dioxide. 
The  samples  of  air  for  analysis  for  carbon  dioxide  were 
collected  in  large,  round-bottom  flasks,  varying  in  capac- 
ity from  2000  cubic  centimeters  to  2600  cubic  centimeters, 
made  especially  for  the  purpose. 

Experiments  proved  that  titrations  could  be  made 
much  more  accurately  in  round-bottom  flasks  than  in  the 
Erlenmeyer  flasks  usually  employed,  since  the  faintest 
pink  color  could  readily  be  detected  by  giving  the  flask  a 
rotary  motion  and  observing  the  color  through  the  depth 
of  the  liquid  as  it  spread  in  a  thin  film  upon  the  sides  of  the 
flask. 

Each  flask  was  provided  with  a  well-fitting,  two-hole 
rubber  stopper,  fitted  with  glass  plugs.  Before  being  used, 
the  flasks  were  boiled  with  sulphuric  acid  to  remove  any 
free  alkali  which  may  have  been  present,  and  then  carefully 
rinsed  and  standardized. 

139 


140 


THE  AIR  AND   VENTILATION  OF   SUBWAYS 


Six  of  these  flasks  were  fitted  into  a  basket,  which  was 
carried  by  the  collector.  A  large  football  pump,  with  the 
valve  reversed,  to  pump  air  from  the  flasks,  was  employed ; 
and  this,  with  about  10  feet  of  rubber  tubing,  a  ther- 


mometer, and  a  notebook,  completed  the  collector's  outfit. 
This  apparatus  is  shown  in  Fig.  22. 

When  it  was  desired  to  collect  a  sample,  the  basket  was 
opened  and  the  stopper  removed  from  one  of  the  flasks. 
The  free  end  of  the  rubber  tubing  was  then  inserted  into 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


141 


the  flask  as  far  as  the  bottom.  This  done,  the  operator 
removed  to  a  distance  with  his  pump  and  pumped  air  from 
the  flask  for  about  four  minutes.  This  amount  of  pumping 
was  capable  of  removing  about  eight  times  the  volume  of 


'§3 


air  in  the  flask,  and  provided  for  the  collection  of  a  proper 
sample. 

After  the  sample  was  collected,  the  stopper  was  replaced 
in  the  flask,  the  temperature  noted,  and  the  data  observed 
which  were  to  fix  the  identity  of  the  sample. 


142        THE  AIR  AND   VENTILATION   OF   SUBWAYS 

The  samples  were  usually  analyzed  on  the  day  of  collec- 
tion or  the  day  after.  Experiments  showed  that  no 
appreciable  change  took  place  by  allowing  a  sample  to 
stand  for  twenty-four  hours  before  analyzing. 

On  its  arrival  at  the  laboratory,  the  flask  was  placed  in  an 
upright  position  on  a  suitable  rest  and  one  of  the  glass  rods 
removed  from  the  stopper.  The  stopper  was  then  gently 
pressed  down  until  it  reached  a  point  marked  on  the  neck 
of  the  flask  at  which  its  capacity  had  been  calibrated. 

A  pipette  was  next  inserted  through  the  hole  in  the 
stopper  and  20  cubic  centimeters  of  standard  barium 
hydroxide,  to  absorb  the  C02,  allowed  to  flow  into  the 
flask  with  a  few  drops  of  plenolphthalein.  (See  Fig.  23.) 
The  solution  was  allowed  to  stand,  with  occasional  shak- 
ing, for  one  hour. 

The  delivery  tube  of  a  special  burette  was  then  inserted 
into  the  flask  through  one  of  the  holes  in  the  stopper,  and 
the  excess  of  barium  hydroxide  titrated  with  standard 
oxalic  acid.  (See  Fig.  24.)  The  glass  rod  in  the  second 
hole  of  the  stopper  was  removed  from  time  to  time  to 
relieve  the  pressure.  One  cubic  centimeter  of  this  oxalic 
acid  was  equivalent  to  one-tenth  of  a  cubic  centimeter  of 
carbon  dioxide.  From  the  quantity  of  barium  hydroxide 
used,  the  amount  of  carbon  dioxide  in  the  original  sample 
of  air  was  calculated,  the  volume  being  reduced  to  0 
degrees  Centigrade  and  760  millimeters  pressure. 

Although  the  barium  hydroxide  solution  remained  prac- 
tically constant  from  day  to  day,  it  was  always  stand- 
ardized before  each  series  of  analyses. 

The  oxalic  acid  employed  for  making  up  the  standard 
solution  was  tested  by  titrating  with  standard  potassium 
permanganate  and  found  to  be  satisfactorily  pure. 

The  bottle  in  which  the  standard  solution  of  barium 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  143 

hydroxide  was  kept  was  provided  with  a  safety  bottle 
containing  pumice  and  caustic  soda  and  a  rubber  bulb, 
which  forced  the  liquid  up  into  the  pipette. 


FIG.  24.  Apparatus  for  carbon  dioxide  analyses.   Method  of  titration  with 
oxalic  acid  after  the  absorption  of  the  carbon  dioxide  by  barium  hydroxide. 

The  burette  used  for  titration  was  especially  made  for 
the  purpose,  and  had  a  delivery  tube  9  centimeters  long, 
which  in  use  projected  well  into  the  flask  of  air. 


144         THE   AIR   AND   VENTILATION   OF   SUBWAYS 


Inasmuch  as  the  manner  in  which  the  sample  was  col- 
lected gave  room  for  some  error  if  the  collector  was  inatten- 
tive or  careless  in  his  work,  care  was  taken  to  collect  check 
samples  from  time  to  time  by  the  help  of  other  assistants. 
This  error  was  further  guarded  against  by  entrusting  the 
collections  only  to  persons  who,  by  age  and  training, 
seemed  certain  to  use  proper  care.  One  of  the  collectors 
held  the  rank  of  assistant  engineer  under  the  Municipal 
Civil  Service  Commission  of  the  city.  Another  was  an 
analytical  chemist  of  long  experience. 

A  sample  of  air  which  was  taken  to  check  the  work  of  a 
collector  gave  the  following  results : 


Conditions  of  experiment. 

Parts  CO.,  per 
10,000  volumes 
of  air. 

Collector's  sample  

3.54 

Samples  collected  as  a  check 

3  48 

Difference  

.06 

Experiments  were  made  to  determine  whether  or  not 
long  standing  of  the%  barium  hydroxide  solution  in  contact 
with  the  flask  would  have  any  effect  on  the  results.  For 
this  purpose  four  samples  of  outside  air  were  collected  at 
the  same  time  and  place,  and  the  barium  hydroxide  solution 
allowed  to  remain  in  the  flask  for  periods  of  from  one  to 
four  hours.  The  results  follow: 


Conditions  of  experiment. 


Titrated  at  the  end  of  one  hour  . 
Titrated  at  the  end  of  two  hours  . 
Titrated  at  the  end  of  three  hours 
Titrated  at  the  end  of  four  hours . 


Parts  CO2 

per  10,000 

volumes 

of  air. 


3.48 
3.47 
3.49 
3.48 


THE   AIR  OF  THE   NEW   YORK   SUBWAY 


145 


Experiments  to  ascertain  whether  or  not  any  difference 
in  the  results  would  be  obtained  by  adding  the  barium 
hydroxide  to  the  flask  at  the  time  of  collection  gave  results 
which  follow: 


Conditions  of  experiment. 


Solution  added  at  time  of  collection 
Added  four  hours  after  collection 


Parts  CO2 

per  10,000 

volumes 

of  air. 


4.33 
4.36 


Another  set   of   samples   was  taken   and   analyzed   as 
follows : 


Parts  CO2 

No. 

Conditions  of  experiment. 

per  10,000 
volume. 

of  air. 

1 

Added  barium  hydroxide  solution  at  time  of  collection 

2.09 

2 

Added  barium  hydroxide  solution  at  time  of  collection 

3.02 

3 
4 
5 

Added  barium  hydroxide  solution  after  eighteen  hours 
Added  barium  hydroxide  solution  after  eighteen  hours 
Added  barium  hydroxide  solution  after  eighteen  hours 

3.02 
3.11 

(paraffined  stopper) 

3  13 

6 

Added  barium  hydroxide  solution  after  eighteen  hours 

(paraffined  stopper) 

3  22 

Another  set  of  samples  was  analyzed  as  follows : 


Parts  CO2 

No. 

Conditions  of  experiment. 

per  10,000 
volumes 

of  air. 

1 

Added  barium  hydroxide  at  time  of  collection    .    .    . 

3.40 

2 

Added  barium  hydroxide  at  time  of  collection    .    .    . 

3.56 

3 

Added  barium  hydroxide  after  twenty-four  hours.    . 

3.44 

4 

Added  barium  hydroxide  after  twenty-four  hours.    . 

3.57 

146        THE   AIR   AND   VENTILATION   OF   SUBWAYS 

Analyses  for  oxygen.  About  eighty  samples  of  air  were 
analyzed  for  oxygen.  The  difference  between  the  amount 
present  in  the  subway  and  in  the  streets  seemed  so  slight 
and  uninstructive  that  the  determinations  were  soon  dis- 
continued as  a  routine  procedure. 

The  samples  of  air  were  collected  in  glass  tubes  of  300 
cubic  centimeters  capacity,  closed  at  each  end  by  glass 
stopcocks.  The  tubes  were  filled  with  oxygen-free  water 
at  the  laboratory  and  taken  to  the  point  where  the  samples 
were  to  be  collected.  There  the  cocks  were  opened  and  the 
water  allowed  to  flow  out,  the  desired  sample  of  air  taking 
its  place.  The  cocks  were  then  closed  and  the  sample 
taken  to  the  laboratory  for  analysis. 

The  oxygen  was  determined  by  absorption  with  phos- 
phorus, according  to  the  method  of  Lindemann.  Hempel 


JTS  PER  10,000 
BY  VOLUME 

en  os 

1905 

JULY 
0     17      24   8 

AUGUST 
L        7      14     21     2 

SEPTEMBER 

OCTOBER 

NOVEMBER  - 

DECEMBER 
4       11     18    S 

/ 

/ 

r-vV5 

vli£t^ 

x 

X 

/<\ 

v, 

/ 

-- 

X 

-+- 

s 

:  

\ 

X 

1  —  - 

•^ 

t    4 

3^3' 

^^r: 

^ 

-^ 

" 

V'\\ 



X 

| 

FIG.  25.  Weekly  average  carbon  dioxide  in  the  subway  and  streets 
from  July  10  to  December  25,  1905.  The  number  of  determinations 
included  in  this  figure  was  1,772. 

burettes  and  a  Hempel  pipette,  constructed  for  solid 
absorbents,  were  employed.  The  phosphorus  was  specially 
prepared,  and  the  pipette  was  kept  covered  to  protect  it 
from  the  action  of  light.  The  pipette,  when  in  use,  was 
immersed  in  water  to  maintain  a  constant  temperature, 
and  thus  obviate  any  inaccuracy  which  might  have  been 
caused  by  temperature  changes.  (See  Fig.  26.) 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


147 


Carbon  dioxide  results.  The  carbon  dioxide  analyses 
produced  results  from  which  the  author  derived  the  fol- 
lowing conclusions: 


FIG.  26.  Apparatus  for  determining  the  proportion  of  oxygen  in  air. 
The  sample  of  air  to  be  analyzed  was  collected  in  the  receptacle 
which  lies  on  the  floor. 

The  average  amount  of  carbon  dioxide  in  the  subway 
was  a  little  larger  than  the  amount  in  the  air  of  the  streets. 


148         THE   AIR   AND    VENTILATION   OF   SUBWAYS 

The  average  of  all  results  was,  for  the  subway,  4.81 
volumes  per  10,000  volumes  of  air,  and  for  the  streets, 
3.67;  difference,  1.14.  This  difference  must  be  regarded 
as  very  slight.  (See  Fig.  25.) 

The  frequency  with  which  the  air  was  renewed  could 
not  be  accurately  calculated,  for  the  reason  that  the 
number  of  passengers  traveling  in  the  subway  was  not 
known. 

At  no  time  or  place  was  the  amount  of  carbon  dioxide 
large. 

The  greatest  amount  of  carbon  dioxide  found  in  the 
subway  was  8.89.  This  occurred  in  one  of  the  tunnels 
between  the  Grand  Central  station  and  the  33d  Street 
station,  on  December  27,  1905,  at  6.02  P.M.  At  the  same 
time  there  was  a  block  in  the  traffic,  during  which  trains 
were  stalled  at  all  points  in  the  vicinity.  At  the  adjoin- 
ing stations  of  33d  Street  and  Grand  Central,  the  carbon 
dioxide  was  higher  than  usual  at  the  same  time,  the 
amount  at  33d  Street  being  7.84  and  at  Grand  Cen- 
tral 7.87. 

The  carbon  dioxide  in  the  subway  varied  according  to 
season,  hour,  place  where  the  sample  was  collected,  and 
other  circumstances. 

Season.  There  was  more  carbon  dioxide  found  in  the 
autumn  than  in  the  summer  or  winter.  (See  Fig.  27.)  It 
seemed  likely  that  this  was  explainable  largely  on  the 
ground  that  many  more  passengers  were  carried  in  autumn 
than  in  summer,  and  that  in  winter  there  was  more  wind 
in  the  streets  and  the  subway,  increasing  the  amount  of 
ventilation. 

Hourly  variations.  The  amount  of  carbon  dioxide 
varied  in  the  subway  at  different  hours  of  the  day. 
(See  Fig.  28.)  These  irregularities  corresponded  with  the 


THE  AIR  OF  THE  NEW   YORK  SUBWAY 


149 


irregularities  in  the  amount  of  travel  which  took  place  at 
different  hours. 

It  is  interesting  to  note  that  periodic  changes  in  the 


*%*J 


MORNING  HOURS 
7.30-11  A.M. 


FIG.  27.     Carbon  dioxide  at  different  stations  at  different  seasons  during 
the  hours  of  maximum  travel  in  the  morning  and  afternoon. 

amount  of  carbon  dioxide  occurred  in  the  streets.  In  the 
streets  the  carbon  dioxide  was  highest  between  5.30  and 
6  P.M.,  and  lowest  between  1  and  3  A.M.  The  amount 


150        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

increased  from  a  minimum  in  the  early  morning  hours  to 
about  9  A.M.  After  this  there  was  a  fall  to  about  1.30 
P.M.,  followed  by  a  rise  to  the  highest  point  of  the  day, 
which  occurred  between  5.30  and  6  P.M.  The  average 


NIGHT 

6  P.M.-6  A.M. 


FIG.  28.     Hourly  variations  in  the  amount  of  carbon  dioxide  in  the  air  of 
the  subway.     Averages  of  1244  analyses. 


range  of  C02  outside,  as  determined  by  hourly  results,  was 
.8  part  per  10,000. 

In  the  subway  the  greatest  amount  of  carbon  dioxide 
for  the  whole  day  also  occurred  between  5.30  and  6  P.M. 
Thereafter,  there  was  a  gradual  fall  to  the  lowest  point, 
which  was  reached  between  3  and  4  A.M. 

From  this  lowest  point  the  amount  increased  steadily 
to  about  9  A.M.,  after  which  it  fell  irregularly  to  between 
1  and  2  P.M. 

The  average  for  the  whole  day  agreed  closely  with  the 
average  between  1  and  3  P.M. 

In  the  late  afternoon  there  was  a  rapid  rise  to  the  maxi- 
mum for  the  day,  which  was  reached  at  about  5.30  P.M. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


151 


TABLE  IV.  —  SIMULTANEOUS  DETERMINATIONS  OF  CARBON  DIOX- 
IDE AT  AND  BETWEEN  STATIONS  IN  THE  SUBWAY.  THE 
NUMBER  OF  ANALYSES  INCLUDED  IN  THIS  TABLE  IS  442. 


Date,  1905. 

Point  of  observation. 

Carbon 
Dioxide. 

Found  . 

Ex- 
cess. 

July  31-Aug.  4 

July  29-Aug.  5 

July  28-Aug.  2 
July  28-Aug.  1 

Dec.  14-23 

Dec.  14-26 
Dec.  15-22 
Dec.  26-27 
Dec.  15-22 

Dec.  13-21 
Dec.  28 
Dec.  29 

Between  Fulton  Street  and  Brooklyn  Bridge  stations 
Average  for   Fulton   Street   and   Brooklyn    Bridge 
stations          

4.26 

4.07 
4.35 

4.37 
4.13 
4.29 
4.18 
4.47 
4.28 

4.40 
4.57 
4.61 
4.68 
4.77 
4.46 
4.57 
4.17 
4.27 
4.12 
3.99 
4.48 
4.23 
4.73 

4.46 
4.44 
4.27 
4.07 
3.99 
6.31 

6.21 

6.06 
5.92 
6.74 
6.55 
7.21 
6.82 
6.55 

6.21 

4.78 
4.75 
6.18 
5.45 
6.30 
4.58 

.19 

-.02 
-.16 
-.29 

-.12 
-.04 
-.09 
-.11 
-.10 
.13 
.25 

.27 
.17 
.08 

.10 
.14 
.19 
.39 

.34 
.03 
.73 
1.72 

Between  Brooklyn  Bridge  and  Worth  Street  stations 
Average  for  Brooklyn    Bridge  and    Worth    Street 
stations      .'    . 

Between  Worth  Street  and  Canal  Street  stations  . 
Average  for  Worth  Street  and  Canal  Street  stations 
Between  Canal  Street  and  Spring  Street  stations  . 
Average  for  Canal  Street  and  Spring  Street  stations 
Between  Spring  Street  and  Bleecker  Street  stations 
Average  for  Spring  Street  and  Bleecker  Street  sta- 
tions   

Between  Bleecker  Street  and  As  tor  Place  stations 
Average  for  Bleecker  Street  and  Astor  Place  stations 
Between  Astor  Place  and  14th  Street  stations   . 
Average  for  Astor  Place  and  14th  Street  stations 
Between  14th  Street  and  18th  Street  stations    . 
Average  for  14th  Street  and  18th  Street  stations 
Between  18th  Street  and  23d  Street  stations 
Average  for  18th  Street  and  23d  Street  stations 
Between  28th  Street  and  33d  Street  stations      . 
Average  for  28th  Street  and  33d  Street  stations 
Between  33d  Street  and  Grand  Central  stations    . 
Average  for  33d  Street  and  Grand  Central  stations 
Between  Grand  Central  and  Times  Square  stations 
Average  for  Grand  Central  and  Times  Square  sta- 
tions   

Between  Times  Square  and  50th  Street  stations     . 
Average  for  Times  Square  and  50th  Street  stations 
Between  50th  Street  and  59th  Street  stations    .    . 
Average  for  50th  Street  and  59th  Street  stations  . 
Between  Fulton  Street  and  Brooklyn  Bridge  stations 
Average  for  Fulton    Street  and    Brooklyn   Bridge 
stations      .        .        ... 

Between  Canal  Street  and  Spring  Street  stations  . 
Average  for  Canal  Street  and  Spring  Street  stations 
Between  14th  Street  and  18th  Street  stations    .    . 
Average  for  14th  Street  and  18th  Street  stations  . 
Between  33d  Street  and  Grand  Central  stations    . 
Average  for  33d  Street  and  Grand  Central  stations 
Between  Grand  Central  and  Times  Square  stations 
Average  for  Grand  Central  and  Times  Square  sta- 
tions                   .... 

Between  66th  and  72d  Street  stations     .        .    . 

Average  for  66th  Street  and  72d  Street  stations    . 
Under  Central  Park,  south  of  110th  Street  station 
At  110th  Street  station 

Under  Harlem  River 

Mott  Avenue  station  

Mean  CO2  betwe 
Mean  CO2  at  sta 

en  stations 

5.05 

4.87 

.18 

tions   

152        THE  AIR  AND   VENTILATION  OF   SUBWAYS 


-i-3 


--s 


£ 


The  difference  be- 
tween the  least  and 
greatest  amounts  of 
carbon  dioxide  was, 
according  to  these 
hourly  averages,  two 
parts  per  10,000. 

Figure  29  shows  the 
variation  in  the 
amount  of  C02  in  the 
subway  and  streets  as 
determined  by  hourly 
results. 

Differences  in  differ- 
ent parts  of  the  subway. 
There  was  more  carbon 
dioxide  at  express  sta- 
tions than  at  local 
stations,  except  at  the 
especially  open  express 
station  at  96th  Street. 

Among  the  principal 
express  stations,  the 
largest  average  amount 
of  carbon  dioxide  was 
found  at  14th  Street. 
Then  came  the  Brook- 
lyn Bridge,  Grand  Cen- 
tral, 72d  Street,  and 
96th  Street  stations,  in 
the  order  named. 
There  was  more  carbon  dioxide  between  stations  than 
at  the  adjoining  stations,  although  in  most  cases  this 


ooo'oi  MI  sj.avd'soo 


<D     ft 


®  >> 


14— I      fl} 

o   £ 

I* 

§  .• 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


153 


difference  was  very  little.  The  results  of  442  analyses 
showed  this  average  difference  to  have  been  .18  part  per 
10,000,  with  a  range  from  .29  to  1.72.  Data  relating  to 
this  subject  are  given  in  Table  IV. 

Marked  differences  occurred  in  the  amount  of  carbon 
dioxide  found  at  points  above  and  below  50th  Street.  The 
average  of  all  results  which  were  capable  of  being  taken 
into  account  to  show  this  difference  demonstrated  that  the 
air  from  50th  Street  uptown  was  much  purer  than  the  air 
from  50th  Street  downtown.  This  is  shown  in  Table  V. 


TABLE  V. 

CARBON  DIOXIDE  IN  THE  SUBWAY  NORTH  AND  SOUTH  OF 
FIFTIETH  STREET.  THE  NUMBER  OF  ANALYSES  INCLUDED 
IN  THIS  TABLE  IS  1,182. 

FROM    FIFTIETH    STREET    DOWNTOWN. 


1905. 

Brooklyn 
Bridge. 

Spring 
Street. 

Fourteenth 
Street. 

Twenty- 
third 
Street. 

Grand 
Central. 

1.46 
1.61 
1.91 
2.08 

July  14r-Sept.  18 
Sept.  1^-Nov.  16 
Nov.  17-Dec.  5 
Dec.  6-Dec.  30 

1.14 
1.34 
2.17 
2.01 

1.08 
1.03 
1.51 
1.62 

1.39 
1.50 
2.58 
2.37 

0.97 
1.17 
1.77 
1.38 

1.66 

1.31 

1.96 

1.32 

1.76 

FROM    FIFTIETH    STREET    UPTOWN. 


Fiftieth 
Street. 

Fifty- 
ninth 
Street. 

Sixty- 
sixth 
Street. 

Seventy- 
second 
Street. 

Seventy- 
ninth 
Street. 

July  14-Sept.  18 
Sept.  19-Nov.  16 

1.20 
1.26 

.88 
.97 

.31 
.71 

.32 
.86 

.42 
.61 

Nov.  17-Dec.  5 

2.27 

.71 

.63 

.82 

.42 

Dec.  6-Dec.  30 

1.02 

.75 

.52 

.65 

.30 

1.44 

.83 

.54 

.66 

.44 

154        THE  AIR  AND   VENTILATION   OF   SUBWAYS 


Differences  in  the  elevation  above  the  pavement  at 
which  samples  were  taken  made  little  difference  in  the 
amount  of  CO2  found  in  the  subway.  These  differences 
are  indicated  in  Table  VI. 

TABLE  VI 

CARBON    DIOXIDE    AT    DIFFERENT    ELEVATIONS    ABOVE    THE 
PLATFORMS    OF    SUBWAY    STATIONS 


Date, 
1905. 

Place. 

Time. 

Two 
feet. 

Four 
feet. 

Six 
feet. 

Eight 
feet. 

Ten 

feet. 

?a 

<J« 

Aug.  17 
Aug.  18 

Aug.  19 
Aug.  22 
Aug.  23 
Aug.  24 

14th  Street  station  .    . 
Grand  Central  station 
Brooklyn  Bridge  station 
Grand  Central  station 
14th  Street  station  .    . 
Grand  Central  station 
Brooklyn  Bridge  station 

2.00-  2.15P 
9  .  45-10  .  10* 
1.40-  2.15P 
9.35-10.00" 
10.45-11.10* 
10.00-10.30* 
9.55-10.25* 

4.01 
5.35 
4.21 
4.84 
4.72 
4.63 
4.91 

3.48 
4.83 
4.41 
4.61 
4.97 
4.67 
4.92 

4.11 
4.73 
4.36 
4.59 
4.69 
4.74 
4.64 

4.24 
4.71 
4.18 
4.69 
4.90 
4.59 
4.50 

4!73 

4.18 
4.71 
4.60 
4.65 
4.74 

4.05 

4.87 
4.27 
4.69 
4.78 
4.66 
4.74 

4.58 
4.58 

Mean  CO2  at  different  heights 
Mean  of  all  observations     .    .    . 

4.67 

4.58 

4.61 

4.58 

4.55 
4.58 

4.54 

4.58 

4.60 
4.58 



Departu 
mean 

re    of    mean    for   each    height    from 
of  all  observations     

+  .09 

+  .03 

-.03 

-.04 

+  .02 

The  C02  in  the  air  of  the  cars  in  summer,  when  the 
windows  and  front  doors  were  open  and  the  travel  com- 
paratively light,  was  not  far  different  from  the  air  of  the 
subway  itself. 

Oxygen  results.  The  samples  of  air  which  were  analyzed 
for  oxygen  were  collected  from  9.30  A.M.  to  5.30  P.M., 
between  the  Brooklyn  Bridge  and  96th  Street  stations. 

The  average  amount  of  oxygen  found  in  the  air  of  the 
streets  was  20.71  per  cent;  in  the  subway,  20.60  per  cent; 
difference,  .11  per  cent.  The  least  amount  found  in  the 
subway  was  20.25  per  cent. 

BACTERIAL  CONDITION  OF  THE  AIR 

The  studies  concerning  the  microorganisms  in  the  sub- 
way related  chiefly  to  the  number  and  origin  of  the  bacteria 
and  molds.  It  was  not  practicable  within  the  time  and 


THE   AIR  OF  THE  NEW   YORK  SUBWAY 


155 


scope  of  the  investigation  to  determine  the  various  species 
of  bacteria  present,  but  the  principal  sources  of  many  of 
them  were  investigated  indirectly  with  fairly  satisfactory 
results. 


FIG.  30.     Colonies  of  bacteria  grown  on  a  plate  exposed  to  the  air  for 
fifteen  minutes  at  the  Grand  Central  Subway  Station. 

Quantitative  methods  of  analysis.  The  bacteria  were 
collected  by  allowing  them  to  settle  from  the  air  on  cir- 
cular plates,  or  Petri  dishes,  3J  inches,  or  about  9  centi- 
meters, in  diameter,  containing  a  standard  agar  culture 


156         THE  AIR  AND   VENTILATION   OF   SUBWAYS 

medium,  and  by  collecting  them  from  the  air  by  means  of 
sand  filters. 

The  plate  method.  The  plates  containing  the  culture 
medium  were  carried  from  the  laboratory  to  the  points  of 
observation  in  a  handbag.  The  plates  and  covers  were 
fastened  together  by  means  of  elastic  bands,  each  pair 
separated  from  other  pairs  by  sterilized  towels. 

To  make  an  observation,  the  plates  were  taken  from  the 
handbag  and  placed,  usually,  upon  a  bench  about  18  inches 
from  the  pavement.  The  covers  were  then  removed  and 
kept  off  for  fifteen  minutes,  or  a  fraction  of  this  time, 
depending  upon  the  observer's  judgment  of  the  numbers 
which  would  probably  be  found. 

During  the  exposure  of  the  plates,  the  observer  removed 
to  a  distance  and  made  the  notes  necessary  to  identify  the 
observation. 

The  covers  were  then  replaced,  secured  to  their  respective 
dishes  by  the  rubber  bands,  and  returned  to  the  laboratory 
in  the  handbag.  The  plates  were  put  into  the  incubator 
within  two  hours  after  exposure. 

The  plates  were  incubated  at  a  temperature  of  37  degrees 
Centigrade  for  forty-eight  hours.  The  colonies  of  bacteria 
and  molds  which  developed  in  this  time  were  then  counted. 
Care  was  taken  to  separate  the  two. 

Most  of  the  exposures  were  made  at  the  subway  sta- 
tions at  points  as  far  removed  from  draughts  as  possible. 
Exposures  out  of  doors  were  made,  for  the  most  part, 
on  the  line  of  the  subway  beyond  the  influence  of  sub- 
way air,  and  at  an  elevation  of  about  3  feet  above  the 
sidewalk. 

In  all,  about  2800  exposures  were  made. 

The  agar  culture  medium  was  prepared  with  Liebig's 
extract  of  beef  and  5  per  cent  agar. 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  157 

The  reaction  of  the  medium,  after  preliminary  trials  to 
ascertain  the  optimum,  was  fixed  at  J  to  1  per  cent  acid 
to  phenolphthalein.  In  preparing  the  plates  for  use,  10 
cubic  centimeters  of  the  agar  medium  was  poured,  and 
the  plates  then  put  into  the  incubator  for  twenty-four 
hours.  Plates  which  developed  colonies  in  this  time  were 
contaminated  and  not  used. 

All  the  bacteriological  plates  were  exposed  in  duplicate. 
The  results  reported  were  averages  of  the  counts  of  two 
plates  in  every  instance. 

Preliminary  trials  of  different  media  and  at  different 
periods  of  incubation  showed  that  a  gelatin  medium  kept 
for  several  days  at  or  below  what  is  generally  termed 
"  room  temperature  "  would  often  develop  more  colonies 
than  an  agar  medium  developed  at  body  temperature. 
There  were  probably  several  reasons  for  this:  The  higher 
temperature  of  the  body  undoubtedly  kept  many  delicate 
air  organisms  from  growing.  Gelatin  was  a  more  favora- 
ble solidifying  agent  than  agar.  An  incubation  period  of 
more  than  forty-eight  hours  seemed  to  be  essential  to  the 
growth,  to  visible  colonies,  of  some  bacteria  in  artificial 
culture  media. 

The  chief  objection  to  the  gelatin-room-temperature 
method  was  that  gelatin  melted  at  a  temperature  which 
made  it  unsuitable  for  summer  use,  became  too  easily 
liquefied  by  certain  bacteria,  and  was  likely  to  be  too 
rapidly  overgrown  with  molds. 

The  procedure  adopted  seemed  to  be  the  most  practical 
under  the  circumstances.  It  had  also  the  merit  of  being 
capable  of  duplication  at  any  time  and  place  with  a  consider- 
able degree  of  accuracy. 

The  numbers  of  bacteria  which  actually  existed  in  the 
air  must  have  been  largely  in  excess  of  the  numbers  found, 


158        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

but  it  was  not  feasible  to  ascertain  how  great  was  this  dif- 
ference. 

Colonies  of  bacteria  grown  in  a  plate  exposed  for  fifteen 
minutes  to  the  air  at  the  Grand  Central  subway  station 
are  shown  in  Fig.  30. 

The  filter  method.  The  collection  of  microorganisms  by 
the  use  of  filters  provided  means  for  estimating  the  numbers 
of  bacteria  and  molds  recoverable  from  a  measured  volume 
of  air.  After  a  considerable  amount  of  preliminary  work, 
the  method  adopted  was  substantially  that  employed  by 
Sedgwick,  Prudden,  and  others.1 

The  filters  consisted  of  glass  tubes  about  13  centimeters 
long  and  0.5  centimeters  inside  diameter.  At  one  end  the 
filtering  material  was  held  in  place  by  a  small  plug  of 
wire  gauze,  and  at  the  other,  when  the  filter  was  not  in 
use,  by  a  plug  of  cotton. 

Various  filtering  materials  were  tried  in  experiments 
preliminary  to  the  adoption  of  a  standard  method,  especially 
the  sugar  medium  of  Sedgwick,  proposed  before  the  Society 
of  Arts  in  1888.2  In  the  subway  work  the  advantages  of 
a  soluble  medium  were  more  than  offset  by  the  care  with 
which  the  sugar  required  to  be  sterilized  and  kept  dry. 

The  filtering  medium  finally  adopted  was  sand.  The 
depth  of  sand  was  about  5  centimeters.  Most  of  the 
grains  were  about  half  a  millimeter  in  diameter.  The 
particles  were  largely  quartz.  Two  filters  were  always 
arranged  in  tandem.  (See  Fig.  32.) 

Air  was  made  to  pass  through  the  filters,  in  most  cases  by 
means  of  an  exhaust  pump  of  accurate  construction,  whose 
action  had  been  carefully  tested.  Sixty-six  strokes  pumped 

1  Firth,   "  Studies  from  the  Department   of  Pathology,  College  of 
Physicians  and  Surgeons,"  New  York,  Volume  VII,  1900.    (See  Fig.  32.) 

2  Sedgwick  and  Tucker,  "  Methods  for  the  Biological  Examination 
of  Air,"  Proceedings  of  the  Society  of  Arts,  Boston,  1888. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


159 


20  liters,  and  this  was  the  amount  usually  pumped  in  each 
case. 

Where  it  was  not  feasible  to  use  the  air  pump,  a  brass 
vacuum  cylinder  of  about  600  cubic  inches,  or  10  liters, 

a  2 
1* 

11 

p«.2 


o  3 

li 

^5 


If 

si 

1.9 


a 

si 


I 


a  - 


CO    <u  'S 
2  fl 


capacity,  fitted  with  a  pressure  gauge  and  suitable  stop- 
cocks, was  employed,  as  devised  by  Prudden.  The  cylinder 
was  266  centimeters  long  and  177  centimeters  in  diameter, 
and  was  fitted  into  a  neat  leather  bag  with  suitable  open- 


160         THE   AIR  AND   VENTILATION   OF   SUBWAYS 

ings,  through  which  the  gauge  could  be  read  and  the 
filters  connected.     (See  Fig.  31.) 
Before  using  the  cylinder,  the  air  was  exhausted  from  it 


FIG.  32.     Air  pump,  sand  filters  and  other  apparatus  for  bacteriological 

analysis  of  air. 

and  the  stopcocks  closed.  It  was  then  placed  in  the  hand- 
bag and  taken  to  the  place  where  the  observation  was  to 
be  made.  The  filters  were  then  connected  to  the  cylinder 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  161 

by  means  of  short  rubber  tubing,  the  pressure  gauge  read, 
and  the  air  allowed  to  flow  into  the  cylinder  through  the 
filters.  When  the  desired  quantity  of  air  had  been  filtered, 
the  cocks  were  closed,  the  filters  removed,  and  the  gauge 
read. 

Upon  returning  to  the  laboratory  the  sand  was  emptied 
from  the  first  filter  into  a  test  tube  containing  10  cubic 
centimeters  of  sterile  water,  and  thoroughly  agitated. 

The  water,  with  the  organisms  which  had  been  rinsed 
from  the  sand,  was  then  plated  in  agar  and  incubated  for 
forty-eight  hours  at  37  degrees  Centigrade  and  the  colonies 
counted. 

The  second  filter  was  treated  in  the  same  way.  Molds 
were  excluded  from  the  count. 

Another  method,  and  the  one  which  was  adopted  finally, 
discarded  the  use  of  the  distilled  water.  The  sand  from  a 
filter  was  poured  into  a  tube  of  melted  agar,  the  tube 
agitated  and  then  poured  into  a  Petri  dish,  leaving  the  sand 
behind.  A  second  tube  of  agar  was  then  poured  upon 
the  sand  remaining  in  the  first  tube.  This  was  then 
agitated  and  the  agar  and  sand  both  poured  into  a  second 
Petri  dish.  The  two  Petri  dishes  were  then  incubated. 

Most  of  the  bacteria  found  were  caught  in  the  first 
filter. 

Additional  bacterial  work.  Beside  the  routine  estimates 
of  the  number  of  bacteria  recovered  from  the  air,  special 
studies  were  made  of  the  length  of  life  of  the  pneumo- 
coccus  in  the  subway,  the  numbers  of  bacteria  in  subway 
and  other  dusts  (see  Fig.  33),  the  action  of  lubricating  oil 
upon  bacteria,  the  kinds  of  molds  present,  and  the  effi- 
ciency of  various  commercial  deodorants  and  germicides 
intended  for  subway  use. 


162        THE  AIR  AND   VENTILATION  OF  SUBWAYS 


The  longevity  of  the  pnewnococcus.  The  longevity  of 
the  pneumococcus  was  tested  by  drying  upon  a  flat  piece 
of  broken  trap  rock  from  the  roadbed  about  20  cubic  cen- 
timeters of  sputum  from  a  patient  suffering  from  lobar 
pneumonia  in  the  congestive  stage.  The  presence  of  the 


I 


pneumococcus  in  a  viable  condition  was  tested  in  the 
beginning  of  the  experiment  and  at  the  end  of  every  two 
or  three  days.  The  vitality  was  determined  by  culture 
methods  and  by  inoculating  small  portions  of  the  mois- 
tened sputum  into  guinea  pigs. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  163 

The  rock  with  the  dried  sputum  was  taken  into  the 
subway  and  set  upon  the  top  of  a  clean  iron  beam  at  a 
little  distance  from  the  end  of  a  station  platform.  Small 
parts  of  the  mass  were  removed  from  day  to  day  for  exam- 
ination, but  the  main  body  of  sputum  was  not  taken  out 
of  the  subway  until  the  end  of  the  experiment. 

The  numbers  of  bacteria  in  dust.  Specimens  of  dust 
which  had  gathered  upon  recently  painted  beams  and 
other  clean,  dry  surfaces  were  collected  in  large,  sterile  test 
tubes  and  Erlenmeyer  flasks  and  taken  to  the  laboratory. 
Here  a  small,  weighed  portion  of  the  dust  was  mixed  with 
from  50  to  500  cubic  centimeters  sterile  water.  One  cubic 
centimeter,  and  fractions  thereof,  of  the  water  were  then 
sown  in  the  agar  culture  medium  already  described.  The 
agar  was  incubated  for  forty-eight  hours  at  37  degrees 
Centigrade  and  the  colonies  counted.  From  these  counts 
the  numbers  of  bacteria  per  gram  of  dust  were  calcu- 
lated. 

Action  of  oil  on  bacteria.  The  possibility  that  the  lubri- 
cating oil  which  was  copiously  used  in  the  first  few 
months  after  opening  the  subway  might  have  a  germicidal 
or  cultural  effect  upon  bacteria  was  inquired  into. 

Specimens  of  oily  wood,  stone,  and  refuse  paper  from 
the  tracks  were  taken  to  the  laboratory  and  examined  for 
the  numbers  of  bacteria  which  they  contained.  The  oil 
itself  was  tested  for  its  action  upon  various  species  of 
bacteria. 

Kinds  of  molds.  Although  it  was  not  feasible  to  study 
the  kinds  of  bacteria,  because  of  the  great  similarity  in 
their  forms  and  cultural  behavior,  it  was  practicable  to 
determine  a  few  of  the  molds  present.  This  was  done  by 
fishing  from  the  mixed  colonies  of  molds  and  bacteria 
which  developed  upon  the  plates  exposed  in  the  subway. 


164        THE   AIR  AND   VENTILATION  OF  SUBWAYS 

From  specimens  obtained  in  this  way,  pure  cultures  were 
made  upon  various  media  suitable  for  the  propagation  of 
the  molds. 

No  attempt  was  made  to  make  this  work  exhaustive, 
since  it  seemed  doubtful  whether  a  complete  knowledge  of 
the  numbers  and  kinds  of  molds  in  the  subway,  had  it 
been  obtainable,  would  have  thrown  much  light  upon 
the  problems  in  hand. 

Efficiency  of  deodorants  and  disinfectants.  The  efficiency 
of  different  chemical  compounds  advocated  by  various 
persons  to  purify  the  air  of  the  subway  was  examined  into. 
They  were  tested  both  with  reference  to  their  capacity  for 
destroying  unpleasant  odors  and  bacteria. 

The  capacity  of  these  compounds  to  destroy  odors  was 
tested  in  the  laboratory  by  producing  unpleasant  odors  in 
suitable  closed  chambers,  and  then  introducing  the  com- 
pounds in  different  amounts  and  under  different  circum- 
stances of  temperature  and  humidity. 

The  disinfectant  properties  of  the  compounds  were 
tested  by  allowing  them  to  act  upon  bacteria  in  colonies  on 
culture  media,  in  films  and  emulsions,  on  toothpicks,  and 
on  freshly  impregnated  cotton  threads.  The  germs  used 
in  these  experiments  were  the  typhoid  bacillus  and  the 
colon  bacillus,  the  pneumococcus  and  the  Staphylococcus 
pyogenes  albus.  The  laboratory  procedures  were  such  as 
are  usually  employed  in  careful  work  of  this  kind. 

Results.  A  careful  examination  of  the  bacterial  data 
collected  in  these  studies,  excepting  the  data  which  relate 
to  the  dust,  led  the  author  to  the  following  conclusions: 

Numbers  of  bacteria  in  subway  and  streets  compared.- 
There  were,  on  an  average,  more  than  twice  as  many 
bacteria  found  in  the  air  of  the  streets  as  in  the  air  of  the 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


165 


subway,   excepting  after  rains,   when  fewer  were  found 
outside  than  inside. 


3000 


2000 


1000 


FIG.  34.  Average  numbers  of  bacteria  which  subsided  from  the  air  per 
square  foot  per  minute,  as  determined  by  the  plate  method,  in  the 
subway  and  streets  from  July  10  to  October  2,  1906.  The  number  of 
samples  represented  is  2742. 

The  average  numbers  of  bacteria  which  settled  from  the 
air  in  fifteen  minutes,  and  were  subsequently  enumerated, 


3,000 

2,000 

1,000 

0 


Sli 


FIG.  85.  Average  numbers  of  bacteria  which  settled  from  the  air  upon 
each  square  foot  per  minute,  at  different  subway  stations  and  in  the 
streets,  and  were  subsequently  counted.  The  number  of  samples 
represented  is  2753. 

were,  in  the  subway,  500;  outside,  1157;  difference,  657. 
(See  Figs.  34  and  35.) 


166        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

The  average  number  of  bacteria  found  by  filtering  the 
air  was  3200  per  cubic  meter  in  the  subway  and  6500  in  the 
streets;  difference,  3300. 

Molds.  The  molds  recovered  from  the  air  by  filters  were 
almost  always  less  numerous  in  the  subway  than  out  of 
doors.  The  maximum  number  of  molds  found  was  1100 
per  cubic  meter.  This  observation  was  made  in  the  tunnel 
under  Central  Park. 

The  average  ratio  of  molds  to  bacteria,  as  determined  by 
the  observations  with  filters,  Was  1  to  40  in  the  subway. 

Effects  of  wind  in  the  streets.  The  wind  in  the  streets 
had  a  decided  effect  upon  the  numbers  of  bacteria  collected 
from  the  air,  both  inside  and  outside  of  the  subway.  The 
averages  show  that  five  times  as  many  bacteria  were 
recoverable  from  the  air  in  the  streets  with  a  wind  of  18 
miles  per  hour  as  with  a  wind  of  9  miles. 

Origin  of  the  bacteria.  No  attempt  was  made  to  identify 
the  different  kinds  of  bacteria.  To  have  undertaken  to 
name  the  species,  even  with  a  great  deal  more  time  than 
was  available  and  a  special  corps  of  bacteriologists,  would 
probably  have  produced  little  result.  Nevertheless,  the 
conclusion  was  reached  that  most  of  the  bacteria  in  the 
subway  came  from  the  streets.  The  principal  reasons  for 
holding  this  view  follow: 

1.  The  numbers  of  bacteria  recovered  from  the  air  of 
the   subway  varied   with  the  more  decided  changes   in 
numbers  in  the  streets. 

2.  At  the   subway   stations   the  bacteria    were    more 
numerous  near  the  stairways  than  at  the  remote  ends  of 
the  platforms. 

3.  In  the  subway   stations,   the   bacteria   were   more 
numerous  on  that  side  of  the  road  into  which  the  wind 
blew  than  on  the  opposite  side. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  167 

4.  There  were  more  bacteria  at  the  arrival  ends  of  the 
platforms  of  the  stations  than  at  the  departure  ends. 

5.  Street  dirt,   probably  containing  large  numbers  of 
bacteria,  was  often  carried  down  the  stairways  into  the 
subway  by  inrushing  currents  of  air  and  by  the  passengers. 


•v,  *<• 


FIG.  36.  Bacteria  from  the  New  York  Subway  magnified  about  1000  times. 

Although  it  seemed  likely  from  these  reasons  that  most 
of  the  bacteria  in  the  air  of  the  subway  were  derived  from 
the  streets,  there  was  ground  for  concluding  that  some, 
and  among  them  objectionable  kinds  of  bacteria,  were 


168        THE  AIR  AND   VENTILATION   OF   SUBWAYS 


due  to  the  presence  of  the  people.  (See  Fig.  36.)  It  is 
practically  certain  when  great  crowds  are  packed  together, 
as  they  often  were  in  some  stations  and  most  cars,  that 
dangerous  bacteria  are,  at  least  occasionally,  transmitted 
from  person  to  person.  An  obvious  feature  of  this  danger 
lies  in  the  fact  that  people  talk,  cough,  and  sneeze  into 
one  another's  faces  at  extremely  short  range  under  such 
circumstances. 

Effect  of  trains.  The  numbers  of  bacteria  in  the  air  of 
the  subway  varied  with  the  amount  of  travel.  They  were 
most  numerous  when  the  trains  were  most  numerous,  and 
fewest  when  the  trains  were  fewest. 

When  the  trains  were  blocked  many  of  the  bacteria 
disappeared  from  the  air.  In  one  case  the  bacteria  were 
reduced  from  1800  to  250  in  about  an  hour  in  this  way. 
This  is  shown  in  Table  VII. 

TABLE  VII. 

EFFECT  ON  THE  NUMBERS  OF  BACTERIA  IN  THE  AIR  OF  THE 
SUBWAY  PRODUCED  BY  A  BLOCKADE  LASTING  AN  HOUR, 
NOVEMBER  11,  1905 


Place. 

Time. 

Microorganisms 
per  cubic  meter 
of  air. 

Bacteria.      Molds. 

110th  Street  and  Broadway  station,  north  f 
end,  east  platform.     Soon  after  the  col- 
lection   of    the    first    sample    all    trains< 
stopped  running.    Finally,  no  passengers  | 
in  subway 

10.20a 
10.37a 
10.55a 
11.15a 

1,300              0 
750              0 
400              0 
250              0 

Average     

... 

700              0 

Effect  of  sweeping.    The  effect  of  sweeping  the  platforms 
with   brooms,    without    first   taking   precautions   against 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


169 


raising  dust,  was  noted.  On  one  occasion  the  numbers  of 
bacteria  were  increased  by  sweeping  from  about  5000  to 
13,000,  and  remained  above  8000  for  at  least  three-quarters 
of  an  hour  —  the  time  covered  by  the  observation.  The 
effect  of  sweeping  is  shown  in  Table  VIII. 

Effects  on  harmful  microorganisms.  It  was  not  found 
that  any  harmful  germs  were  capable  of  multiplying  in  the 
oil  which  dripped  from  the  machinery  of  the  cars  upon  the 
broken  stone  ballast  and  wooden  ties  of  the  roadbed. 

The  lubricating  oil  apparently  removed  and  collected 
from  the  air  large  numbers  of  bacteria,  many  of  which 
soon  ceased  to  exist. 

The  pneumococcus  was  found  capable  of  retaining  its 
virulence  in  dried  sputum  in  the  subway  for  twenty-three 
days.  This  is  in  marked  contrast  to  the  findings  of  others, 
who  have  reported  that  the  pneumococcus  was  killed  in 
four  hours  in  sunlight. 

TABLE  VIII 

EFFECT  ON  THE  NUMBERS  OF  BACTERIA  IN  THE  AIR  OF  THE  SUB- 
WAY PRODUCED  BY  SWEEPING  THE  PLATFORMS  IMPROPERLY 


Place. 

Time. 

Microorgan- 
isms per 
cubic  meter 
of  air. 

Ratio 
of  bac- 
teria to 
molds. 

Bac- 
teria. 

Molds. 

Fulton  Street  station,  south  end,  west 
platform.     Remote  from  openings  to 
streets 

10.25a 
10.41a 
10.57a 
11.12a 

4,900 
13,200 
8,100 
8,500 

100 
50 
0 
0 

49:  1 
264:  1 

Porter  began  sweeping  near  by     .... 
Still  sweeping,  but  farther  off    . 

Still  sweeping,  middle  of  platform  .    .    . 
Average     

8,600 

38 

226:1 

170        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

With  few  exceptions,  there  were  not  so  many  bacteria  in 
the  air  of  the  toilet  rooms  as  in  the  rest  of  the  subway.  In 
some  cases  the  numbers  were  much  greater. 

Inefficiency  of  proprietary  disinfectants.  The  proprietary 
disinfectants  used  in  the  toilet  rooms  had  no  germicidal  or 
deodorizing  value.  Furthermore,  they  produced  counter 
odors  of  a  peculiarly  unpleasant  character. 

Numbers  of  microorganisms  in  dust.  The  numbers  of 
bacteria  recovered  from  the  dust  of  the  subway  averaged 
500,000  per  gram. 

The  largest  number  of  bacteria  found  in  subway  dust 
was  2,000,000  per  gram.  Still  greater  numbers  probably 
could  have  been  found  by  selecting  the  specimens  of  dust 
toward  this  end. 

For  comparison  with  the  numbers  of  bacteria  found  in 
dust  from  the  subway,  it  is  interesting  to  note  that  dust 
which  had  accumulated  under  similar  circumstances  in  a 
Broadway  theater  contained  270,000  bacteria;  in  a  new 
and  fashionable  hotel,  360,000;  in  a  well-known  Fifth 
Avenue  church,  320,000;  in  the  tallest  office  building  in  the 
city,  850,000;  and  in  the  attic  of  a  country  house  one 
hundred  and  fifty  years  old,  110,000  bacteria  per  gram. 
The  full  results  of  these  analyses  are  given  in  Table  IX. 

Dust  which  had  accumulated  in  the  subway  contained 
over  twice  as  many  molds  as  dust  collected  in  outside 
buildings.  In  the  dusts  the  ratio  of  bacteria  to  molds  was 
89  to  1  for  the  subway,  and  250  to  1  elsewhere. 

ODORS 

Odors  were  more  or  less  prevalent  at  all  times  and  at 
nearly  all  places  in  the  subway.  In  some  cases  they  were 
so  faint  as  hardly  to  be  noticeable,  in  others  very  decided. 

The  effects  of  the  odors  upon  the  passengers  varied  with 


TABLE    IX.  —  NUMBERS    OF    BACTERIA    AND    MOLDS    FOUND    IN 
ACCUMULATED     DUSTS 


Number  of  Microorgan- 

Sam- 

isms per  gram  of 

Ratio  of 

Date, 

i  nn  F: 

Place. 

ple 

dust. 

bacteria 

lyuo. 

No. 

to  molds. 

Bacteria. 

Molds. 

Oct.  23 

96th  Street  station     .    . 

1 

550,000 

1,500 

367:  1.0 

Oct.  24 

Grand  Central  station  . 

2 

1,000,000 

2,500 

400:1.0 

Oct.  25 

14th  Street  station     .    . 

3 

2,000,000 

500 

4,000:  1.0 

Oct.  26 

Wall  Street  station    .    . 

4 

600,000 

4,100 

146:  1.0 

Oct.  26 
Oct.  31 

Brooklyn  Bridge  station 
Columbia  University  sta- 

5 

1,100,000 

6,500 

169:  1.0 

tion             

6 

81,000 

1,600 

51:  1.0 

Nov.  1 

Fulton  Street  station    . 

7 

1,000,000 

3,500 

286:  1.0 

Nov.  2 

South  Ferry  station  .    . 

8 

300,000 

5,600 

54:  1.0 

Nov.  3 

Times  Square  station    . 

9 

160,000 

6,400 

24:  1.0 

Nov.  4 

72d  Street  station  .    .    . 

10 

600,000 

2,900 

07:  1.0 

Nov.  6 

66th  Street  station     .    . 

11 

460,000 

0 

Nov.  8 

125th  Street  and  Lenox 

Avenue  station    .    .    . 

12 

650,000 

6,500 

100:  1.0 

Nov.  9 

Mott  Avenue  station     . 

13 

470,000 

11,000 

43:1.0 

Nov.  10 

149th  Street  and  Third 

Avenue  station    .    .    . 

14 

440,000 

8,700 

51:  1.0 

Nov.  11 

110th  Street  and  Broad- 

way station  

15 

290,000 

6,000 

48:  1.0 

Nov.  13 

Columbus  Circle  station 

16 

190,000 

1,100 

173:  1.0 

Nov.  14 

23d  Street  station  .    .    . 

17 

160,000 

2,300 

70:     .0 

Nov.  15 

Grand  Central  station  . 

18 

650,000 

550 

1,182:    .0 

Nov.  16 

14th  Street  station     .    . 

19 

500,000 

17,000 

29:    .0 

Nov.  17 

Brooklyn  Bridge  station 

20 

370,000 

11,000 

34:    .0 

Nov.  18 

Wall  Street  station    .    . 

21 

270,000 

12,000 

23:     .0 

Nov.  20 

50th  Street  station     .    . 

22 

150,000 

11,000 

14:    .0 

Nov.  21 

South  Ferry  station  .    . 

23 

120,000 

4,200 

29:  1.0 

Nov.  22 

96th  Street  station     .    . 

24 

340,000 

5,000 

68:  1.0 

Nov.  23 
Nov.  24 

Brooklyn  Bridge  station 
Times  Square  station    . 

25 
26 

800,000 
370,000 

8,300 
2,200 

96:  1.0 
168:  1.0 

Nov.  25 

Grand  Central  station  . 

27 

650,000 

2,300 

283:  1.0 

Nov.  27 

14th  Street  station     .    . 

28 

300,000 

14,500 

21:  1.0 

Dec.  5 

South  Ferry  station  .    . 

31 

51,000 

3,900 

13:  1.0 

Dec.  6 

Canal  Street  station  .    . 

34 

230,000 

6,500 

37:1.0 

Dec.  4 

Attic  of  house  150  years 

old,  Hadley,  Mass.     . 

29 

120,000 

6,300 

19:  1.0 

Dec.  4 

Attic  of  house  150  years 

old,  Hadley,  Mass. 

32 

110,000 

5,600 

20:  1.0 

Dec.  4 

Cellar    of    old    Hadley 

house  

33 

52,000 

120,000 

1:2.3 

Dec.  7 

A  fashionable  hotel    .    . 

35 

360,000 

4,400 

82:  1.0 

Dec.  7 

A  Fifth  Avenue  church 

36 

320,000 

5,800 

35:  1.0 

Dec.  8 

A  Broadway  theatre 

37 

270,000 

0 

.  .  . 

Dec.  9 

A  downtown  restaurant 

38 

1,200,000 

0 

.  .  . 

Dec.  9 

Twentieth    floor    of    an 

office  building  .... 

39 

850,000 

1,500 

567:  1.0 

Dec.  9 

Public  ward  of  hospital 

40 

600,000 

2,600 

231:  1.0 

Average  of  thirty  subway  observations 

500,000 

5,600 

89:  1.0 

Average  of  six  New  York  buildings  . 

600,000 

2,400 

250:  1.0 

171 


172        THE   AIR  AND   VENTILATION  OF   SUBWAYS 

the  sensitiveness  of  the  individual.  To  some  persons  the 
odors  were  exceedingly  offensive,  to  others  they  were 
barely  noticeable;  many  passengers  soon  became  used  to 
the  odors  and  did  not  seriously  object  to  them. 

To  persons  unaccustomed  to  the  subway  the  odors  were 
unpleasant,  and  suggested  that  conditions  existed  which 
were  injurious  to  health. 

The  odors  were  most  apparent  during  hot,  damp  weather, 
at  places  where  the  greatest  crowding  occurred  and  where 
the  least  amount  of  ventilation  took  place. 

Odors  were  far  more  often  offensive  in  the  cars  than 
elsewhere,  especially  in  the  fall  and  winter  months,  when 
the  windows  were  closed  and  the  number  of  passengers  was 
unusually  large. 

Methods  of  investigation.  An  effort  was  made  to  ascer- 
tain the  main  causes  of  the  odors.  It  was  not  possible  to 
look  for  them  chemically  or  to  measure  them  by  other 
means  than  the  senses,  although  samples  of  subway  dust 
and  air,  when  brought  to  the  laboratory,  often  smelt  unmis- 
takably of  the  subway.  By  inspections  in  the  subway 
and  repair  shops,  by  examining  in  the  laboratory  a  large 
number  of  solid  and  liquid  substances  taken  from  the 
subway,  and  by  attempting  to  duplicate  the  odors  in 
closed  chambers  under  different  conditions  of  tempera- 
ture and  humidity,  some  of  the  causes  of  the  odors  were 
discovered. 

Results  of  investigating  the  causes.  The  following  con- 
clusions were,  in  the  author's  view,  justified  by  these 
studies : 

Stone  ballast.  The  stone  ballast  of  the  roadbed  was 
responsible  for  part  of  the  odor.  This  stone  was  made  of 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  173 

broken  trap  rock,  and  its  peculiarly  slaty  odor  in  the  warm 
atmosphere  of  the  subway  was  unmistakable.  It  could 
be  most  easily  distinguished,  especially  at  the  more  open 
stations,  on  damp  days. 

Frequently  the  odor  of  the  trap  was  masked  by  other 
odors. 

Lubricants.  The  oil  used  in  lubricating  the  wheels  and 
machinery  of  the  cars  was  one  of  the  principal  causes  of 
odor.  Large  quantities  of  this  oil  were  allowed  to  drip 
from  the  machinery  upon  the  ballast  and  ties  of  the  road- 
bed when  the  subway  was  first  put  in  operation. 

Samples  of  the  oil  were  obtained  for  experiment.  It 
was  not  feasible  to  determine  by  analysis  its  exact  com- 
position, but  in  other  ways  it  was  ascertained  that  it  was 
composed  chiefly  of  petroleum  and  fish  oil. 

The  quantity  of  oil  used  in  the  subway  in  the  first  year 
of  operation  appears  to  have  been  larger  than  had  ever 
been  used  on  an  equal  length  of  road.  It  amounted  to 
over  200  gallons  per  mile  of  road  per  month. 

In  addition  to  this  oil,  about  150  pounds  of  gear  grease 
were  used  per  mile  per  month. 

Much  of  the  oil  and  grease  was  heated  on  the  bearings, 
and  some  of  it  was  volatilized.  The  car  journals,  motor 
armature  bearings,  and  motor  axle  bearings  were  some- 
times raised  to  a  temperature  of  from  100  to  170  degrees 
Fahrenheit. 

That  the  oil  was  distributed  through  the  atmosphere  of 
the  subway  was  fully  demonstrated.  It  was  recovered 
from  the  dust  by  extraction  with  ether  to  the  extent  of 
1.18  per  cent  by  weight  of  dust. 

Results  of  evaporation  tests  of  the  lubricating  oil, 
according  to  the  method  of  Gill,  are  given  in  the  tables  on 
following  page. 


174        THE  AIR  AND   VENTILATION  OF  SUBWAYS 


LOSS  IN  WEIGHT   OF   SUBWAY   OIL   BY   EVAPORATION  —  AIR  TEM- 
PERATURE 


Sample  No. 

Per  cent  loss 
four  hours  at 

after  twenty- 
25-29.9°  C. 

1 
2 
3 

0.31 
0.35 
0.45 

Average 


0.37 


LOSS   IN  WEIGHT   OF    SUBWAY   OIL   BY   EVAPORATION  —  TEMPER- 
ATURE   OF    PARTS    LUBRICATED 


Wheel  Journals. 

Axle  Bearings. 

Sample  No. 

Per  cent  loss  after 
eight  hours  at 
74-76°  C. 

Per  cent  loss  after 
eight  hours  at 
110-115°  C. 

1 
2 
3 
4 
5 

1.57 
1.08 
1.86 
1.86 

6.93 
8.04 
7.65 
7.77 
9.22 

Average 

1.59 

7.92 

It  will  be  noted  that  at  air  temperature  there  was  a  loss 
of  0.37  per  cent  and  7.92  per  cent  at  110  and  115  degrees 
Centigrade.  Under  similar  conditions  whale  oil,  high  grade 
fish  and  rape  seed  oils  showed  gains  of  from  1.01  to  5.39 
per  cent  at  74  and  76  degrees,  and  losses  of  0  to  2.65  per 
cent  at  110  and  115  degrees,  respectively. 

Motors.  Odors  were  given  off  by  the  hot  motors  acting 
upon  various  more  or  less  volatile  substances  other  than 
oil  and  grease.  Among  these  substances  were  the  insulat- 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  175 

ing  material  covering  some  of  the  electric  wiring  and  the 
paint  upon  the  motor  cases. 

Electric  sparking  produced  the  odors  of  ozone  and 
nitrous  oxide. 

The  hot  brake  shoes  gave  off  a  peculiar  odor. 

Disinfectants.  A  pungent  and  unpleasant  odor  was 
produced  by  the  proprietary  disinfectants  used  in  the 
toilet  rooms.  This  odor  was  so  penetrating  that  it  was 
occasionally  noticeable  on  the  streets  outside  of  the  subway. 

Tile  cement.  A  strong  and  disagreeable  odor  was 
caused  by  an  oily  cement  used  in  fastening  decorative  tiles 
in  place  at  some  of  the  stations.  An  ingredient  of  this 
cement  was  a  cheap  grade  of  fish  oil.  In  order  to  disguise 
the  fishy  odor,  creosote  was  freely  mixed  with  the  oil 
before  mixing  it  with  the  cement.  The  result  of  these 
intermingled  odors  was  peculiarly  unpleasant.  Fortu- 
nately, the  odor  of  the  cement,  although  very  powerful 
at  first,  rapidly  disappeared. 

Hot  boxes.  Hot  boxes,  of  which  there  were  a  con- 
siderable number  when  the  road  was  first  put  in  operation, 
at  times  produced  a  persistent  and  suffocating  odor.  Wool 
waste  was  used  in  packing  the  car  journals,  and  when  this 
caught  fire  its  unpleasant  smell  could  be  distinguished 
through  the  subway  for  a  long  time. 

Fuses.  Occasionally  a  fuse  was  blown  out  and  its 
odor  was  distributed  up  and  down  the  line.  When  a  fire 
occurred,  as  happened  on  a  few  occasions,  the  odor  of  smoke 
persisted  in  the  part  of  the  subway  where  the  fire  occurred 
for  a  surprisingly  long  period  of  time.  In  one  case  the  odor 
was  distinctly  noticeable  to  passengers,  as  the  cars  passed 
the  spot,  three  months  after  the  fire  had  taken  place. 

Tobacco  smoke.  The  odor  of  tobacco  smoke  was  not 
uncommon  at  the  subway  stations.  Rules  existed  against 


176         THE   AIR   AND   VENTILATION   OF   SUBWAYS 

smoking  in  the  subway,  but  they  were  not  enforced. 
Lighted  cigars,  cigarettes,  and  pipes  were  occasionally 
carried  even  into  the  cars. 

Concrete  and  fresh  paint.  Odors  from  new  concrete  and 
fresh  paint  were  often  noticed.  The  former  was  persistent, 
the  latter  transient. 

Odors  of  human  origin.  Odors  of  human  origin  were 
sometimes  present,  but  almost  always  close  to  people. 
They  were  most  common  during  warm,  damp  weather  and 
where  there  was  much  crowding.  These  odors  often  came 
from  the  clothing  of  the  passengers.  It  was  sometimes 
possible  to  learn  the  occupation  of  a  workman  by  the  odor 
of  his  clothes.  Odors  of  coffee,  garlic,  bad  teeth,  liquor, 
cheese,  and  perfumery  were  some  of  the  personal  odors 
noticed. 

The  peculiar  odor  given  off  by  clothing  which  had  been 
hung  in  a  kitchen  was  frequently  noticed. 

In  fact,  under  the  conditions  of  crowding,  amounting 
frequently  to  close  personal  contact,  it  seemed  that  odors 
of  practically  every  character  connected  with  human 
existence  were  noticeable. 

Excepting  in  rare  instances,  where  ignorant  employees 
were  not  kept  under  as  strict  supervision  as  their  defective 
sense  of  decency  required,  the  odors  which  permeated  the 
general  air  of  the  subway  did  not  point  to  conditions 
dangerous  to  health.  Personal  odors  were  detectible  only 
at  short  range.  When  people  are  crowded  so  closely 
together  that  their  breath  and  other  body  odors  are  offen- 
sive, there  is  always  danger  that  disease  may  be  trans- 
mitted  from  one  to  another. 

The  toilet  rooms  were  much  neglected  at  the  time  cf 
this  investigation,  and  often  gave  rise  to  an  unpleasant 
local  odor. 


THE  AIR  OF  THE  NEW   YORK  SUBWAY 


177 


DUST 


The  dust  of  the  subway  was  made  the  subject  of  study 
because  of  its  unpleasant  features  and  the  possibility  that 
it  might  play  a  part  in  producing  or  aggravating  respiratory 


FIG.  37.  Physical  appearance  of  dusts.  1.  From  a  fashionable  hotel. 
2.  From  the  street  (Broadway).  3.  From  a  popular  theatre.  4.  From 
the  subway. 

diseases.    Its  possibilities  for  harm  were  to  lie  perhaps  in 
its  bacterial  and  physical  composition. 


178        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

Methods  of  examination.  The  dust  was  examined 
microscopically,  chemically,  and  bacteriologically,  by  a 
special  method  which  was  devised  for  determining  the 
gross  weight  of  dust  in  a  measured  volume  of  the  air, 
and  by  an  instrument  for  estimating  the  total  number  of 
floating  particles  present. 

Microscopical  and  chemical  examination.  The  micro- 
scopical analyses  were  intended  to  show  the  shape  of  the 
particles  and  what  could  be  ascertained  in  this  way  con- 
cerning their  physical  composition.  The  dust  was 
examined  under  low  powers  of  the  microscope  and  with 
magnifications  as  high  as  1200  diameters. 

It  was  possible,  by  means  of  a  common  horseshoe  magnet 
held  beneath  a  piece  of  paper  sprinkled  with  the  dust,  and 
slowly  moved  from  side  to  side,  to  distinguish  particles  of 
iron  and  steel.  These  metal  particles  could  be  made  to 
rise  on  edge  and  reverse  their  position  by  changing  the 
pole  of  the  magnet  presented  to  them. 

The  chemical  analyses  were  intended  to  indicate  the 
amount  of  iron,  organic  matter,  silica,  and  oil. 

Bacteriological  examination.  The  bacteriological  analy- 
ses were  intended  to  give  some  idea  of  the  numbers  of 
bacteria  and  molds  present  in  dusts  which  collected  at 
different  points.  (Fig.  43.)  The  bacteriological  method 
employed  in  this  work  has  already  been  sufficiently 
explained. 

Weight  of  dust  in  air.  At  first  the  gross  weight  of 
dust  in  a  measured  volume  of  air  was  determined  with 
a  sugar  filter,  through  which  air  was  exhausted  by  means 
of  an  air  pump.  The  amount  of  air  which  it  was  desirable 
to  pass  through  the  filter  proved  to  be  too  great  for  an  air 
pump  of  ordinary  capacity.  After  experimenting  with 
nearly  every  pump  and  blower  on  the  market  which  prom- 


THE   AIR  OF  THE   NEW   YORK  SUBWAY 


179 


ised  to  serve  the  purpose,  a   small  Root's  blower  was 
employed,  the  blower  being  operated,  as  an  exhaust,  by 


FIG.  38.     Dust  collected  on  a  white  tile  exposed  at  the  59th  Street  sub- 
way station  for  one  week. 

hand,  by  means  of  a  crank.  A  test  meter,  manufactured 
by  the  American  Meter  Company,  New  York,  was  used 
to  measure  the  air.  The  meter  was  examined  and 


180        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

found  to  be  accurate  to  within  1J  per  cent  when  used 
in  this  way. 

The  filter  consisted  of  10  cubic  centimeters  of  finely 
granulated  sugar,  contained  in  a  glass  funnel  of  2.5  centi- 
meters diameter,  with  straight  upper  sides.  The  sugar 
rested  upon  a  plug  of  wire  gauze  and  was  5  centimeters 
deep. 


FIG.  39.     Aitken's  koniscope  to  determine  the  number  of  ultimate  dust 
particles  in  air. 

It  was  customary  to  pump  50  cubic  feet,  or  1416  cubic 
meters,  of  air  through  a  filter  for  each  observation. 

The  apparatus  was  so  connected  that  the  air  passed  first 
through  the  filter,  next  through  the  meter,  and  finally 
through  the  Root's  blower,  which  was,  of  course,  run 
backward  in  order  to  obtain  the  exhaust.  This  apparatus 
is  shown  in  Fig.  40. 

When  the  filter  reached  the  laboratory,  the  sugar  was 
carefully  emptied  into  a  beaker  of  distilled  water.  After 
the  sugar  was  dissolved,  the  dust  particles  which  remained 
were  collected  in  a  weighed  Gooch  filter  containing  a  felt 


THE  AIR  OF  THE  NEW   YORK  SUBWAY  181 

of  asbestos.  The  filter  was  then  washed  with  distilled 
water,  dried  at  a  temperature  of  100  degrees  Centigrade, 
cooled,  and  again  weighed.  The  increase  in  weight  was 
taken  to  be  the  weight  of  the  dust.  From  the  data  so 
obtained,  the  weight  of  dust  in  milligrams  per  cubic  meter 
of  air  was  calculated. 

Ultimate  number  of  dust  particles.  The  number  of 
ultimate  particles  of  dust  was  estimated  by  means  of  a 
koniscope,  the  invention  of  Professor  John  Aitken,  F.R.S. 
A  portable  form  of  this  instrument  was  imported  from 
Glasgow  for  the  purpose. 

The  koniscope  has  not  been  so  much  used  in  sanitary 
investigations  as  its  merits  deserve,  and  a  few  words  may 
be  desirable  concerning  it.  It  consists  essentially  of  a 
brass  tube  closed  at  both  ends  by  glass  disks.  Attached  to 
the  tube,  near  one  end,  is  an  air  pump  with  suitable  con- 
nections and  stopcocks.  (See  Fig.  39.) 

To  estimate  the  number  of  particles  of  dust,  the  instru- 
ment was  taken  to  the  place  where  the  atmosphere  was  to 
be  examined.  Air  was  pumped  freely  through  the  tube. 
The  stopcock  connecting  the  tube  with  the  outside  air  was 
then  closed.  A  rapid  stroke  of  the  pump  made  a  partial 
vacuum  in  the  tube,  and  this  rarification  produced  a  cloud 
or  fog  which  could  be  distinctly  seen  by  pointing  the 
tube  toward  the  light  and  looking  through  one  of  the 
glass  disks  at  the  ends.  The  dust  particles  served  as 
nuclei  about  which  the  moisture  condensed  and  so  formed 
the  fog. 

The  depth,  color,  and  intensity  of  the  fog  indicated  the 
number  of  dust  particles  present.  Professor  Aitken  has 
invented  a  more  elegant  and  exact,  but  less  portable,  dust 
counter  with  which  the  koniscope  can  be  standardized. 


182         THE   AIR   AND   VENTILATION   OF   SUBWAYS 

This  more  refined  apparatus  was  tried  in  the  subway,  but 
without  wholly  satisfactory  results.  It  was  very  delicate 
in  respect  to  adjustment,  and  required  a  better  light  than 


was  obtainable.  The  approximate  number  of  particles 
was  usually  estimated  with  the  koniscope  from  the  appear- 
ance of  the  fog,  and  in  accordance  with  the  table  kindly 
supplied  by  Professor  Aitken. 


THE  AIR  OF  THE  NEW  YORK    SUBWAY  183 

Results.  The  studies  of  dusts  led  to  the  following  con- 
clusions : 

Physical  character  of  the  dust.  In  appearance,  the  dust 
was  always  black  and  very  finely  powdered.  It  was 
easily  distinguishable  by  the  eye  from  dusts  collected  in 
the  streets,  and  in  theaters,  churches,  office  buildings, 
and  mercantile  and  manufacturing  establishments.  (See 
Fig.  37.) 

The  subway  dust  had  a  peculiarly  adhesive  character, 
which  caused  it  to  attach  itself  securely  to  all  surfaces, 
even  when  these  were  vertically  placed  and  glazed.  Dust 
collected  on  a  white  tile  exposed  at  the  59th  Street  subway 
station  is  shown  in  Fig.  38.  All  parts  of  the  subway 
which  had  not  recently  been  cleaned  and  painted,  or  were 
not  of  a  dark  color,  were  sprinkled  with  this  black  dust 
when  the  investigation  began. 

The  dust  had  a  marked  capacity  for  soiling  linen  and 
other  articles  of  clothing.  Straw  hats  and  the  light- 
colored  garments  worn  by  passengers  of  both  sexes  in 
summer  were  likely  to  be  soiled  by  coming  in  contact  with 
even  small  accumulations  of  the  dust. 

When  examined  microscopically,  the  dust  was  found  to 
be  composed  of  particles  of  many  substances,  conspicuous 
among  which  were  fine,  flat  plates  of  iron.  In  fact,  these 
iron  particles  could  often  be  seen  with  the  naked  eye, 
glistening  upon  the  hats  and  garments  of  persons  who  had 
been  riding  in  the  subway. 

Particles  two  millimeters  long  were,  on  one  occasion, 
taken  from  a  magnet  which  had  been  carried  in  the  hand  on 
a  ride  of  twenty  minutes  in  the  cars.  By  comparison,  it  was 
found  that  magnets  hung  up  in  the  subway  collected  more 
particles  of  iron  than  magnets  of  the  same  size  and  strength 
hung  up  in  an  iron  foundry  or  a  dry  grinding  and  polishing 


184        THE   AIR  AND   VENTILATION   OF   SUBWAYS 


Ipi 

"•'.:  +t* 

:      *\.*% 

**%>'         •  ,, 

?j$i^-** 


, 
/V ;f^\NVJ^  *-.'.''>  f 


FIG.  41.  Magnetic  field  formed  by  subway  dust.  A  piece  of  paper 
was  laid  on  top  of  a  common  horse  shoe  magnet  and  subway  dust 
was  sprinkled  on  the  paper. 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


185 


establishment.  Figure  41  shows  a  magnetic  field  formed 
by  subway  dust. 

The  size,  as  well  as  the  number,  of  the  particles  depended 
upon  the  place  where  they  were  found. 

Many  were  so  small  that  they  floated  in  the  air  as  dust. 
These  generally  escaped  notice,  except  where  beams  of 
sunlight  entered  the  subway  or  where  the  subway  air 
emerged  from  some  small  opening  into  the  sunlight  in  the 
streets,  under  which  circumstances  they  glistened  plainly. 

Particles  of  subway  dust,  not  iron,  comprised  bits  of 
silica,  cement,  stone,  fibers  of  wood,  wool  and  cotton,  molds, 
and  undistinguishable  fragments  of  refuse  of  many  kinds. 

Besides  the  dust  which  resulted  from  the  grinding  of 
metals,  it  was  evident  that  the  gradual  wear  and  tear  of 
many  substances  in  the  subway  contributed  to  the  dust. 

TABLE  X 

RESULTS     OF     CHEMICAL    ANALYSES     OF     ELEVEN     SAMPLES     OF 
ACCUMULATED    DUST    FROM    THE    SUBWAY 


Silica, 

Volatile 

Date, 
1905. 

Place. 

Total 
iron. 

etc., 
insol- 
uble in 
acids. 

Oil. 

and  or- 
ganic 
matter. 

Per 

Per 

Per 

Per  cent. 

cent. 

cent. 

cent. 

Aug.  3 

96th  Street  station  .... 

63.07 

12.79 

0.88 

23.26 

Aug.  3 

14th  Street  station  .... 

41.77 

26.39 

1.43 

30.41 

Aug.  14 

Grand  Central  station     .    . 

67.35 

12.65 

1.23 

18.77 

Aug.  18 

23d  Street  station     .... 

54.36 

20.50 

0.99 

24.15 

Aug.  17 
Aug.  21 

Brooklyn  Bridge  station    . 
33d  Street  station     .... 

45.72 
69.66 

21.79 
12.34 

1.97 
0.91 

30.52 
17.09 

Aug.  21 

Canal  Street  station    .    .    . 

74.78 

9.46 

0.80 

14.96 

Sept.  19 

1  16th  Street  and  Lenox  Ave- 

nue station     .           .    . 

66.69 

13.84 

0.96 

18.51 

Sept.  19 

Times  Square  station  .    .    . 

68.42 

7.45 

1.00 

23.13 

Sept.  20 

18th  Street  station  .... 

59.84 

17.94 

1.43 

20.79 

Sept.  20 

28th  Street  station  .... 

62.58 

16.28 

1.42 

19.72 

Average 

61.30 

15.58 

1.18 

21.94 

186        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

Chemical  composition  of  the  dust.  The  separate  chemical 
analyses  of  eleven  samples  of  accumulated  dust  from  the 
subway  showed  the  following  average  percentage  com- 
position: total  iron,  61.30,  including  59.89  metallic  iron; 
silica,  etc.,  15.58;  oil,  1.18;  organic  matter,  21.94,  as  shown 
in  Fig.  42.  The  results  in  full  are  given  in  Table  X. 

Origin  of  metallic  dust.  A  large  part  of  the  metallic 
iron  came  from  the  wear  of  the  brake  shoes  upon  the  steel 
rims  of  the  wheels  of  the  cars. 

The  Wear  upon  the  brake  shoes  was  very  severe.  By 
weighing  them  when  they  were  new  and  after  they  were 
worn  out,  and  determining  the  number  used,  it  was  calcu- 
lated by  the  operating  company  that  1  ton  of  brake  shoes 
was  ground  up  every  month  for  each  mile  of  subway. 

The  brake  shoes  consisted  of  cast  iron  with  steel 
inserts. 

There  was  also  some  loss  to  the  rails  and  rims  of  the 
wheels  and  to  the  contact  shoes  which  ran  upon  the  third 
rail.  Probably  25  tons  per  month  would  be  a  low  estimate 
of  the  weight  of  iron  and  steel  ground  up  in  the  whole 
subway  every  month. 

Weight  of  dust  in  subway  and  street  air  compared.  The 
average  weight  of  dust  found  in  the  subway  by  the  use  of 
the  sugar  niters,  using  all  of  the  results,  was  61.6  milligrams 
per  thousand  cubic  feet  of  air,  or  2.25  milligrams  per  cubic 
meter;  in  the  streets,  52.1  milligrams  per  thousand  cubic 
feet,  or  1.83  milligrams  per  cubic  meter;  difference,  9.5 
milligrams.  The  maximum  amount  found  in  the  subway 
was  204  milligrams. 

Twenty-three  comparative  tests  were  made  to  deter- 
mine with  particular  care  the  weight  of  dust  per  thousand- 
cubic  feet  of  air  inside  of  the  subway  and  in  the  streets  at 
the  same  time  and  as  near  the  same  place  as  possible. 


THE  AIR  OF  THE  NEW   YORK  SUBWAY 


187 


These  showed  an  excess  of  dust  in  the  subway  of  47  per 
cent  over  that  outside.  In  five  cases  there  was  more  dust 
outside,  the  greatest  excess  being  30  per  cent.  In  the 
other  eighteen  cases  the  excess  of  subway  dust  over  street 
dust  ranged  from  11  to  800  per  cent. 

Weight  of  dust  inhaled  by  passengers.    The  weight  of 
dust  which  the  average  passenger  inhaled  in  one-half  hour 


FIG.  42.    Composition  of  subway  dust  as  determined  by  chemical  analysis 
of  eleven  samples. 


in  the  subway  was  very  slight.  Assuming  that  360  cubic 
centimeters,  or  22  cubic  inches,  of  air  were  taken  in  at  each 
breath  and  that  the  passenger  breathed  eighteen  times  a 


188        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

minute,  the  total  quantity  of  air  which  passed  into  the 
lungs  in  half  an  hour  was  about  6.88  cubic  feet,  or  6.50 
cubic  meters.  Using  the  average  of  all  results,  or  61.6 
milligrams  per  thousand  cubic  feet,  as  the  weight  of  dust 
suspended  in  the  atmosphere,  it  appears  that  the  average 
passenger  took  into  his  nose  or  mouth  .42  milligrams  of 
dust  in  a  ride  of  half  an  hour. 

Variations  in  the  amount  of  dust.  The  amount  of  dust 
found  in  the  air  of  the  subway  varied  with  a  number  of 
circumstances. 

More  dust  was  found  at  the  arrival  ends  than  at  the 
departure  ends  of  the  station  platforms.  This  was  prob- 
ably due  to  the  fact  that  the  brakes  were  applied  near  the 
arrival  ends,  and  to  the  fact  that  the  currents  of  air  from 
incoming  trains  helped  to  carry  dust  from  those  sections 
of  the  subway  which  lay  between  stations  to  the  plat- 
forms. 

The  stations  where  the  greatest  weights  of  dust  were 
found  were  express  stations;  there  the  amount  of  metallic 
dust  formed  by  the  braking  of  the  trains  was  much  greater 
than  at  the  local  stations  and  the  travel  from  the  streets 
greatest. 

Bacteria.  The  numbers  of  bacteria  found  in  the  dust  of 
the  subway  were  usually  smaller  than  the  numbers  found 
in  dust  which  had  accumulated  outside. 

The  average  result  of  thirty  samples  of  dust  which  had 
accumulated  in  the  subway  was  500,000  bacteria  per  gram 
of  dust.  The  average  obtained  from  six  samples  of  dust 
which  had  accumulated  under  what  appeared  to  be  com- 
parable circumstances  in  different  buildings  in  New  York 
was  600,000. 

The  largest  number  of  bacteria  found  in  a  sample  of 
subway  dust  was  2,000,000. 


THE  AIR  OF  THE  NEW  YORK   SUBWAY  189 

CONCLUSIONS 

A  review  of  the  results  of  the  investigation  so  far  war- 
rants the  following  brief  statement  of  the  most  essential 
facts  determined  with  respect  to  the  quality  of  the  air. 

According  to  usual  sanitary  standards,  based  on  chemical 
and  bacteriological  analyses,  the  general  air  of  the  subway 
was  always  and  everywhere  satisfactory.  The  air  in  the 
cars  is  not  included  in  this  statement. 

According  to  public  opinion,  based  on  the  testimony  of 
the  senses,  the  air  was  everywhere  unsatisfactory,  especially 
during  the  summer  months. 

The  author's  own  conclusion  was  that  the  general  air, 
although  disagreeable,  was  not  actually  harmful,  except, 
possibly,  for  the  presence  of  iron  dust.  The  strong 
draughts  in  winter  at  the  stations  and  the  lack  of  sanitary 
care  exercised  over  the  subway  were,  however,  worthy  of 
careful  consideration  in  this  connection. 

The  high  temperature  of  the  subway  was  its  most  notice- 
ably objectionable  feature.  Had  it  not  been  for  the  heat, 
it  is  probable  that  the  other  unpleasant  features  would  have 
failed  to  arouse  serious  protest.  The  heat,  as  is  well 
known,  was  due  to  the  conversion  of  electric  power  into 
friction.  The  amount  of  heat  given  off  by  the  passengers 
was  so  small  by  comparison  as  to  have  had  practically 
nothing  to  do  with  elevating  the  general  temperature. 

The  heat  was  most  objectionable  in  the  mornings  and 
evenings  of  summer  during  the  hours  of  greatest  travel 
and  when  the  air  outside  was  cooler  than  during  the  rest  of 
the  day. 

The  heat  did  not  indicate  that  the  air  was  vitiated  or 
stagnant,  as  was  popularly  supposed.  The  subway  was 
hot  because  a  great  deal  of  heat  was  produced  in  it,  and 
stored  by  the  materials  of  which  the  subway  was  built. 


190        THE   AIR   AND   VENTILATION   OF   SUBWAYS 

That  the  heat  did  not  escape  rapidly  enough  for  comfort 
was  no  proof  that  the  air  was  not  renewed  often  enough 
for  health. 

The  carbon  dioxide  and  oxygen  analyses  indicated  that 
the  products  of  respiration  were  rapidly  carried  away. 
Among  the  2200  carbon  dioxide  determinations,  most  of 
which  were  made  in  the  subway,  no  sample  of  air  was  taken 
which  contained  above  8.89  parts  of  C02  per  ten  thousand 
volumes,  and  this  amount  was  found  under  circumstances 
which  must  be  regarded  as  exceptional. 

The  average  excess  of  carbon  dioxide  in  the  subway  over 
that  in  the  streets,  1.14  parts  per  ten  thousand  volumes, 
showed  that  the  air  was  renewed  with  remarkable  frequency. 
In  the  absence  of  a  census  giving  the  number  of  passengers 
in  different  parts  of  the  subway  at  different  hours,  it  was 
impossible  to  calculate  just  how  frequently  the  air  was 
renewed;  but  from  such  estimates  as  it  was  possible  to 
make  it  seemed  not  improbable  that  the  air  of  the  whole 
subway  was  completely  renewed  at  least  every  half  hour. 

It  is  true  that  the  renewal  occurred  somewhat  more 
frequently  in  some  parts  of  the  subway  than  in  others,  but 
the  exchange  was  always  and  everywhere  abundant.  We 
must  except,  of  course,  from  this  statement,  the  cars  when 
crowded  and  closed,  and  other  places  where  dense  crowd- 
ing occurred. 

The  controlling  condition  which  regulated  the  extent  to 
which  the  air  was  renewed  was  the  freedom  with  which  it 
was  forced  in  and  out  of  the  subway.  The  air  was  best 
where  the  subway  was  most  open  to  the  streets,  and, 
conversely,  it  was  least  satisfactory  where  the  subway  was 
most  enclosed.  More  blow-holes  would  have  greatly 
improved  the  conditions. 

The  movement  of  the  trains  set  in  motion  the  essential 


THE  AIR  OF  THE  NEW  YORK  SUBWAY 


191 


ventilating  currents.  This  they  did,  first,  by  forcing 
subway  air  out  and  bringing  street  air  in  at  openings;  and 
second,  by  moving  the  air  through  the  subway  between 
openings. 

It  was  fully  demonstrated  that  there  were  no  pockets  or 
other  places  where  air  stagnated.    Diffusion  was  every- 


FIG.  43.     Colonies  of  bacteria  from  the  dust  of  the  New  York  subway. 

where  rapid,    complete,   and   satisfactory.    The  cars   are 
excepted  in  these  statements,  as  already  indicated. 

The  fact  that  there  were  only  about  half  as  many  bacteria 
found  in  the  air  of  the  subway  as  in  the  air  of  the  streets 


192         THE  AIR  AND  VENTILATION  OF  SUBWAYS 


THE  AIR  OF  THE  NEW  YORK  SUBWAY  193 

under  which  the  subway  ran  gave  ground  for  the  opinion 
that  the  bacteriological  condition  of  the  subway  air  was 
satisfactory,  although  too  much  reliance  should  not  be 
placed  upon  this  guide  to  its  condition.  Judgment  on  this 
point  would  have  been  more  conclusive  had  it  been  possible 
to  demonstrate  that  no  more  harmful  bacteria  existed  in 
the  subway  than  in  the  air  outside.  This  was  beyond  the 
practicable  possibilities  of  bacteriological  technique. 

The  odors  of  the  subway,  like  the  heat  and  dust,  were 
objectionable,  apparently,  chiefly  because  they  were  disa- 
greeable. They  resulted  largely  from  the  operation  of  the 
trains.  They  were,  in  the  author's  opinion,  to  a  large 
extent  preventable. 

The  sanitary  significance  of  the  characteristic  black  dust 
of  the  subway,  containing,  as  it  did,  over  61  per  cent  of 
metallic  particles,  remained  to  be  considered  at  the  close 
of  this  part  of  the  investigation. 


CHAPTER  VII 

HEALTH   OF  NEW  YORK  SUBWAY  EMPLOYEES 

THIS  chapter  is  practically  identical  with  a  report  made 
in  May,  1907,  to  the  Board  of  Rapid  Transit  Commissioners 
for  the  City  of  New  York,  and  describes  an  investigation 
by  the  author  into  the  possible  effects  of  the  metallic  dust 
of  the  first  New  York  subway  on  the  health  of  the 
employees. 

Thanks  are  due  to  many  persons  for  help.  The  Inter- 
borough  Rapid  Transit  Company,  through  Mr.  Frank 
Hedley,  General  Manager,  granted  requests  for  informa- 
tion concerning  the  men  and  furnished  the  100  employees 
who  were  examined. 

The  physical  examinations  and  analyses  were  made  with 
much  skill  by  Dr.  James  Alexander  Miller,  Instructor  in 
Physical  Diagnosis  at  the  College  of  Physicians  and 
Surgeons,  assisted  by  Doctors  H.  C.  Hanscom,  J.  M. 
O'Connor  and  I.  0.  Woodruff.  In  the  autopsies  and  sub- 
sequent histological  examinations  thanks  are  due  to  Dr. 
J.  H.  Larkin,  Adjunct  Professor  of  Pathological  Anatomy, 
and  to  coroner's  physicians  Doctors  T.  D.  Lehane  and  P. 
F.  O'Hanlon.  To  Dr.  Frank  B.  Mallory,  Associate  Pro- 
fessor of  Pathology,  Harvard  Medical  School,  who  collected 
records  to  show  the  pleurisy  found  in  1008  autopsies  per- 
formed at  the  Boston  City  Hospital,  the  author  is  also 
indebted.  Finally,  a  number  of  eminent  pathologists  and' 
medical  practitioners  aided  the  work  by  valuable  council, 
suggestions  and  opinions. 

194 


HEALTH  OF  SUBWAY  EMPLOYEES  195 

PLAN  OF  THE  INVESTIGATION 

It  was  intended  that  the  investigation  should  be  made 
so  as  to  detect  any  physiological  effects  which  might  be 
caused  by  the  dust  of  the  subway,  whatever  they  might  be. 
Special  care,  however,  was  taken  to  look  for  early  signs 
of  more  serious  disease  of  the  lungs,  which  exists  to  an 
excessive  extent  among  persons  engaged  in  dusty  occupa- 
tions. Sufficient  time  had  not  elapsed  since  the  subway 
was  opened  to  reveal  the  symptoms  of  pneumokoniosis 
had  this  condition  existed,  but  it  was  hoped  that  if  this 
disease  was  progressing  some  sign  of  it  could  be  detected. 

Physical  examinations  were  made  of  a  sufficient  number 
of  subway  employees  to  determine  the  condition  of  the 
average  man.  Supplementary  to  these,  bacteriological 
and  chemical  analyses  were  made  of  their  sputum,  urine 
and  sweat. 

To  compare  the  physical  condition  of  the  subway  men 
with  that  of  persons  not  engaged  in  subway  work,  exam- 
inations were  made  of  200  men  representing  twenty  dif- 
ferent occupations. 

To  help  arrive  at  an  understanding  of  the  possible  effects 
of  the  subway  dust,  data  referred  to  in  the  first  part  of 
this  investigation  were  collated  concerning  its  chemical 
composition,  physical  properties,  and  the  weight  of  dust 
in  a  given  volume  of  subway  air.  The  bacteria  associated 
with  this  dust  were  also  considered. 

The  condition  of  the  air  and  the  work  of  the  men  were 
compared  with  the  conditions  which  exist  in  such  vocations 
as  stonecutter,  knife  grinder,  metal  polisher,  and  other 
dusty  occupations  in  which  a  high  mortality  occurs. 

It  being  desirable  to  obtain  an  accurate  understanding 
of  the  anatomical  condition  of  the  men,  and  as  this  could 
be  had  only  by  dissecting  their  bodies  after  death,  arrange- 


196       THE   AIR  AND   VENTILATION   OF   SUBWAYS 

ments  were  made  to  have  as  many  autopsies  as  practicable 
performed  upon  the  remains  of  employees  killed  by  accident 
in  the  subway  during  the  period  covered  by  the  investiga- 
tion. 

Light  was  thrown  upon  the  frequency  with  which  pleurisy 
was  found  at  autopsy  by  reviewing  the  records  of  a  large 
number  of  reports  of  post-mortem  examinations  made 
elsewhere. 

THE  CONDITION  OF  THE  AIR 

Investigations  which  had  been  made  for  the  Board  from 
July,  1905,  to  January,  1906,  showed  that  the  chemical 
condition  of  the  air  of  the  subway,  in  spite  of  unpleasant 
odors  and  heat,  was  remarkably  good. 

The  carbon  dioxide,  as  determined  by  2084  analyses 
covering  practically  all  times  and  places,  was  found  to  be 
but  little  higher  in  the  subway  than  in  the  streets:  the 
average  for  the  subway  was  4.81,  and  for  the  streets  3.67. 
These  figures  represent  parts  of  carbon  dioxide  in  10,000 
volumes  of  air. 

There  was  ample  oxygen.  The  average  of  eighty  anal- 
yses gave  20.60  per  cent  of  oxygen  for  the  subway  as 
against  20.71  per  cent  for  the  streets. 

The  analyses,  checked  by  observations  of  air  currents, 
indicated  that  the  atmosphere  of  the  subway  was  com- 
pletely renewed  at  least  every  half  hour  before  any 
material  change  had  been  made  in  the  methods  of 
ventilation. 

Summarizing  the  opinions  which  the  author  formed  at 
the  conclusion  of  that  investigation,  the  principal  pos- ' 
sibilities  for  harm  in  the  air,  aside  from  rapid  changes  of 
temperature  and  strong  draughts,  lay  in  the  presence  of 


HEALTH   OF   SUBWAY  EMPLOYEES  197 

the    black    metallic    dust.    The    principal   characteristics 
of  this  dust  will  now  be  described. 

Physical  and  Chemical  Composition  of  the  Dust.  When 
examined  microscopically  the  dust  was  found  to  be  com- 
posed of  particles  of  many  substances,  including  innu- 
merable fine,  flat  plates  of  iron.  The  seiron  particles  could 
be  seen  by  a  sharp  eye  glistening  upon  the  hats  and 
garments  of  persons  after  a  short  ride  in  the  subway. 
The  clothing  of  the  employees  gathered  this  dust,  and 
their  hands,  bodies,  and  linen  became  discolored  with  it. 

Large  particles  of  iron  could  readily  be  seen  at  the  sta- 
tions, upon  the  roadbed.  A  common  horseshoe  magnet  sus- 
pended at  the  breathing  line  would,  in  a  few  days,  collect 
a  surprisingly  large  amount  of  iron  dust.  Of  two  magnets 
hung  up  —  one  at  the  Grand  Central  Station  of  the  sub- 
way, and  another  in  a  dry-grinding  establishment,  the  sub- 
way magnet  collected  by  far  the  most  dust.  (See  Fig.  44.) 

Eleven  samples  of  subway  dust  were  analyzed  chemically, 
with  results  given  in  Table  X,  page  185. 

A  glance  at  this  table  shows  that  the  average  amount  of 
iron  in  the  dust  was  61.3  per  cent.  The  samples  were 
collected  from  smooth,  clean  surfaces  upon  which  the  dust 
had  been  allowed  to  settle  from  the  air. 

In  addition  to  the  iron  particles,  the  dust  contained  bits 
of  silica,  cement,  stone,  fibers  of  wood,  wool,  cotton,  silk 
and  other  textile  materials,  molds,  and  indistinguishable 
fragments  of  refuse  of  many  kinds,  resulting  from  the  wear 
and  tear  of  the  subway  and  clothing  of  the  passengers.  In 
fact,  everything  in  the  subway  susceptible  of  wear  con- 
tributed to  the  dust.  In  addition,  refuse  from  the  streets 
was  carried  into  the  subway  by  inflowing  currents  of  air 
and  by  passengers. 


198        THE  AIR  AND   VENTILATION   OF  SUBWAYS 

Bacterial  composition  of  the  air  and  dust.  On  the 
whole,  the  numbers  of  bacteria  found  in  the  dust  of  the 
subway  were  smaller  than  the  numbers  found  in  dust 
from  the  streets.  The  average  obtained  on  analyzing 
thirty  samples  of  dust  from  the  subway  was  500,000  per 
gram  of  dust.  The  average  number  found  on  analyzing 
141  samples  of  subway  air  was  3200  per  cubic  meter. 
These  figures  were  about  one-half  as  large  as  were  found 
for  the  streets. 

These  numbers  represent  bacteria  capable  of  growing  on 
beef-extract-agar,  of  J  to  1  per  cent  acid  reaction  to  phe- 
nolphthalein,  at  the  temperature  of  the  body  and  at  such 
a  rate  that  colonies  could  be  counted  at  the  end  of  forty- 
eight  hours. 

There  was  reason  for  believing  that  some  of  the  bacteria 
in  the  subway  were  more  harmful  than  those  generally 
found  outside.  The  absence  of  sunlight  in  the  subway 
prolonged  the  life  of  the  germs  of  some  diseases.  The 
pneumococcus,  believed  to  be  the  cause  of  lobar  pneumonia, 
was  found  by  experiment  to  be  capable  of  living  twenty-one 
days  in  the  subway  as  against  four  days  in  the  streets. 

The  lack  of  enforcement  of  the  city  ordinance  against 
spitting  and  the  frequency  with  which  passengers  and 
employees  expectorated  upon  the  tracks,  platforms,  and 
stairways,  increased  the  danger  from  tuberculosis 
and  other  respiratory  diseases.  The  excessive  crowding 
exposed  the  employees,  particularly  those  holding  the 
grades  of  guard  and  conductor,  to  still  greater  danger  of 
infection. 

Sources  of  the  iron  dust.  A  large  part  of  the  metallic 
dust  came  from  the  wear  of  the  brake  shoes  upon  the  steel 
rims  of  the  wheels  under  the  cars.  It  was  calculated  that 


HEALTH  OF  SUBWAY  EMPLOYEES       199 

one  ton  of  brake  shoes  was  ground  up  on  every  mile  of  the 
subway  every  month.  In  addition,  there  was  some  loss  of 
metal  from  the  rails,  especially  at  the  curves.  So  great 
was  this  wear  that  an  especially  durable  steel  was  at  length 
made  to  withstand  it. 

The  rims  of  the  wheels  and  the  contact  shoes  which 
supplied  the  motors  under  the  cars  with  electricity  from 
the  third  rail  contributed  some  weight  of  metal  to  the  dust. 
Probably  twenty-five  tons  would  be  a  low  estimate  of  the 
total  weight  of  iron  and  steel  ground  up  in  the  twenty-one 
miles  of  subway  every  month. 

It  must  not  be  supposed  that  all  of  this  great  amount  of 
ground  iron  floated  in  the  air.  Some  of  the  pieces  were  so 
large  that  they  fell  immediately  to  the  track  and  remained 
there.  Others  were  raised  only  for  brief  moments  by 
violent  eddies  produced  by  the  trains.  Large  quantities 
were  caught  by  the  ties  and  broken  stone  ballast,  which 
were  continuously  sprinkled  with  lubricating  oil  from  the 
trains. 

Many  of  the  particles  were  so  greasy  that  they  adhered 
firmly  to  whatever  surfaces  with  which  they  happened 
to  come  in  contact.  The  smallest  and  probably  the 
freshest  particles  remained  longest  in  the  air.  It  was  these 
which  constituted  most  of  the  dust  used  in  the  analyses. 
It  was  these  which  were  breathed. 

Some  dust  was  carried  up  into  the  streets  by  air  currents 
which  were  forced  out  through  the  station  stairways  and 
blow-holes  by  the  trains.  The  trains  also  kept  some  dust 
in  suspension  in  the  subway.  Had  there  been  no  trains 
the  dust  would  have  quickly  settled  from  the  air.  This  is 
shown  by  the  bacteriological  experiment  recorded  in  Table 
VII,  page  168,  in  which  the  bacteria  acted  like  exceedingly 
minute  dust  particles. 


200        THE  AIR  AND   VENTILATION   OF   SUBWAYS 

Weight  of  dust  in  air.  The  average  weight  of  dust  in 
subway  air  was  found  to  be  61.6  milligrams  per  thousand 
cubic  feet  of  air,  or  2.25  milligrams  per  cubic  meter.  This 
was  somewhat  more  than  was  found  in  the  streets  under 
parallel  conditions.  The  figures  for  the  streets  were  52.1 
milligrams  per  thousand  cubic  feet,  or  1.83  milligrams  per 
cubic  meter.  The  average  for  the  subway  was  made  up 
of  the  results  of  146  analyses  made  at  points  and  at  times 
especially  selected  to  give  a  correct  knowledge  of  the  normal 
conditions. 

These  analyses  show  that  the  total  amount  of  dust  in  all 
the  air  contained  in  the  subway  at  any  time  from  the  96th 
Street  station  to  the  Brooklyn  bridge  was  3J  pounds.  The 
dust  was  not  quite  evenly  distributed  through  the  air. 
There  was  more  at  express  stations  than  elsewhere.  At 
any  given  station  there  was  more  dust  at  the  arrival  ends 
of  the  platforms  than  at  the  departure  ends.  These 
differences  were,  however,  slight. 

Weight  of  dust  inhaled.  The  weight  of  dust  which  an 
employee  took  into  his  mouth  or  nose  during  the  course 
of  a  day  of  ten  hours  could  be  computed  from  the  results 
of  the  analysis  just  referred  to.  Assuming  that  360  centi- 
meters or  22  cubic  inches  of  air  were  taken  in  at  each 
breath,  and  that  the  employee  breathed  at  the  average  rate 
of  eighteen  times  per  minute,  the  total  quantity  of  air 
which  passed  into  his  lungs  in  ten  hours  was  6.86  cubic 
feet,  or  .19425  meter.  Taking  61.6  milligrams  per  thou- 
sand cubic  feet  as  the  weight  of  dust  suspended  in  the 
atmosphere,  it  is  found  by  calculation  that  an  employee 
took  into  his  nose  or  mouth  8.4  milligrams  of  dust  in  ten 
hours.  This  is  3066  milligrams  per  year,  or  forty-six 
grains.  It  will  be  shown  presently  that  only  a  small  part 
of  this  could  get  into  the  lungs. 


HEALTH  OF  SUBWAY  EMPLOYEES       201 

Reliable  data  are  lacking  to  show  the  weight  of  dust 
which  exists  in  the  air  of  steel-grinding  and  other  establish- 
ments where  pneumonokoniosis  is  produced  by  dust. 
Hesse  found,  some  years  ago,  from  72  to  100  milligrams 
of  dust  in  a  cubic  meter  of  air  in  an  iron  foundry,  and 
14  milligrams  per  cubic  meter  in  the  air  of  an  iron  mine. 

The  dangers  of  the  dust.  The  possibility  that  the  dust 
might  cause  injury  to  the  eyes,  to  the  skin,  and  to  the 
respiratory  apparatus  was  considered  in  this  investiga- 
tion; but  the  condition  of  the  throats  and  lungs  of  the 
employees  received  the  largest  share  of  attention. 

Injurious  properties  of  subway  dust.  Inasmuch  as  dust 
may  do  harm  in  many  ways,  it  may  be  well  to  describe 
briefly  how  the  subway  dust  was  regarded  in  its  relation 
to  the  health  of  the  subway  employees. 

Chemical  composition.  There  was  nothing  about  the 
chemical  composition  of  iron  particles  to  make  them 
especially  dangerous.  Iron  is  not  like  lead  and  other 
poisonous  substances  in  this  respect.  If  the  subway  dust 
had  been  composed  of  silica,  probably  its  action  would 
have  been  no  different. 

Mere  quantity.  The  amount  of  dust  breathed  was  not 
great  enough  to  be  injurious  solely  on  account  of  its 
bulk.  In  this  respect  the  atmosphere  of  the  subway  was 
wholly  unlike  that  of  flour  mills  and  cement  mills.  There 
the  quantity  was  vastly  greater. 

Bacteria.  Dust  when  breathed  may  cause  disease  by 
carrying  bacteria  into  the  throat  and  lungs.  This  was  a 
matter  worthy  of  some  attention,  in  view  of  bacteriological 
conditions  in  the  subway  already  described.  Particles  of 
dust  which  carry  or  accompany  harmful  bacteria  are 
among  the  most  injurious  kinds  of  dust. 


202       THE  AIR  AND  VENTILATION  OF  SUBWAYS 

Mechanical  or  physical  composition.  Dusts  whose  con- 
sistency most  resembles  that  of  the  organs  which  they 
invade  are  least  harmful,  so  far  as  physical  composition  is 
concerned,  and  the  more  jagged  in  outline  and  resistant  in 
texture  they  are,  the  greater  is  the  capacity  of  the  parti- 
cles to  do  harm.  They  irritate  the  delicate  organs  with 
which  they  come  in  contact,  and  so  open  the  way  for  the 
entrance  of  pathogenic  microbes.  The  most  injurious  of  all 
dusts  are  composed  of  such  substances  as  iron  and  steel. 

So  far  as  the  subway  dust  was  examined,  the  mechanical 
and  bacterial  conditions  were  of  most  interest. 

Contributing  factors.  Various  factors  predispose  persons 
to  respiratory  dust  diseases.  Among  these  may  be  men- 
tioned : 

1.  The  existence  of  some  respiratory  disease  already, 
as,  for  example,  tuberculosis. 

2.  Predisposition  to  respiratory  disease,  whether  this 
predisposition    is    inherited    or    constitutional,    increases 
susceptibility. 

3.  A  neurotic  condition,  in  which  the  person  anticipates 
or  expects  evil  effects  to  follow  the  inhalation  of  a  dusty 
atmosphere,  increases  the  liability. 

4.  Exertion,  requiring  the  breathing  of  unusually  large 
quantities  of  air,  bringing  into  the  lungs  more  dust,  must 
be  recognized  as  a  contributing  factor.    Mouth  breathing 
may  be  included  in  this  category. 

5.  Humid  air,  draughts,  or  an  atmosphere  in  which  rapid 
changes   of   temperature   occur,   contribute  to   the   evil 
possibilities  of  dust. 

6.  An  especially  severe  use  of  the  voice  is  unfavorable. 
Of  all  these  factors,  the  amount  of  air  breathed,  the* 

atmospheric  changes,   and  the  severe  use  of  the  voice 
seemed  to  be  especially  worthy  of  consideration. 


HEALTH  OF  SUBWAY  EMPLOYEES       203 

Natural  defenses  against  dust.  In  normal  health  the 
delicate  structure  of  the  lungs  is  protected  in  various  ways 
against  the  entrance  of  dust  particles  from  the  air: 

1.  The  nose  and  throat  are  themselves  effective  barriers. 
Only  a  very  small  proportion  of  the  dust  particles  which 
enter  the  mouth  or  nose  escape  the  moist  and  irregular 
channels  which  lead  to  the  throat. 

2.  If  a  particle  passes  the  mouth  or  nose,  it  is  almost 
certain  to  be  arrested  by  the  mucous  membrane  of  the 
trachea  and  lower  air  passages.    Here  myriads  of  moving 
cilia  carry  it  to  a  point  from  which  it  can  be  removed  by 
the  conscious  mechanism  of  coughing. 

3.  If  the  particles  go  further  they  enter  the  bronchioles, 
and  from  these  pass  to  the  air  cells  of  the  lungs. 

4.  When  particles  of  dust  reach  the  air  cells  they  do  not 
necessarily  pass  into  the  tissues.    They  do  so  only  when 
they  penetrate  the  endothelium  with  which  these  cells  are 
lined. 

Minute  foreign  substances  may,  however,  be  taken  into 
the  tissues  before  reaching  the  air  cells  of  the  lungs, 
especially  when  the  normal  activity  of  the  mucous  mem- 
brane is  reduced.  This  is  not  uncommon  among  persons 
who  breathe  a  dusty  atmosphere.  When  particles  are 
absorbed,  whether  in  the  throat  or  lungs,  they  generally 
enter  the  lymphatics  and  are  retained  by  the  nodes,  or 
filtering  arrangements,  with  which  the  lymphatic  system 
is  provided.  Only  hi  rare  instances  do  foreign  particles 
penetrate  through  the  lymphatic  system  to  the  blood. 

Infection  through  pathogenic  microbes  occurs  when  the 
protective  barriers  peculiar  to  the  surfaces  of  the  delicate 
mucous  lining  of  the  air  passages  become  injured  and  the 
natural  resistance  toward  them  is  reduced.  It  is  not 
improbably  due  largely  to  the  constant  irritation  produced 


204        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

by  dust  upon  the  mucous  membranes  that  respiratory 
diseases  are  so  common  among  city  dwellers. 

Condition  of  throats  and  lungs  of  city  dwellers.  Respira- 
tory diseases  are  extremely  common  among  persons  who 
live  in  cities,  pneumonia  being  frequently  recorded  as  the 
leading  cause  of  death,  with  tuberculosis  following  closely. 
Bronchitis  and  laryngitis  are  equally  common,  though  less 
fatal,  and  pharyngitis  and  rhinitis  still  more  prevalent. 
The  minor  affections  not  infrequently  lead  to  the  more 
serious  ones. 

When  examined  after  death,  the  lungs  of  city  people  can 
easily  be  distinguished  from  those  of  dwellers  in  the  country, 
the  bright,  rosy  color  which  is  natural  to  the  latter  being 
changed  to  gray  and  sometimes  black  by  particles  of  soot 
and  dust  which  have  gotten  into  them  from  the  air. 

Mingled  with  the  dust  in  the  lungs  of  all  city  dwellers 
are  particles  of  iron.  So  great  is  the  wear  of  iron,  par- 
ticularly from  the  wheels  of  vehicles,  the  brakes  of  street 
and  elevated  railway  cars,  and  the  shoes  of  horses,  that  it 
was  impossible  during  this  investigation  to  find  a  single 
specimen  of  dust  in  New  York  which  did  not  contain 
particles  of  metallic  iron.  Iron  particles  were  collected 
from  the  surface  of  fresh  snow  on  Liberty  Island  in  the 
center  of  New  York  Bay,  a  mile  or  more  from  the  nearest 
land,  thirteen  days  after  an  earlier  snowstorm  had  covered 
the  ground  and  kept  dust  from  being  blown  from  places 
where  it  had  settled.  White  marble  buildings  in  New 
York  lose  their  original  color  within  a  year  and  become 
noticeably  yellow.  The  amount  of  iron  dust  which  gets 
into  the  lungs  is  extremely  small,  but  it  can  be  detected' 
with  certainty  by  the  microscope  and  by  analysis. 

It  seems  unnecessary  to  refer  to  other  dusty  particles 


HEALTH  OF   SUBWAY  EMPLOYEES  205 

which  get  into  the  lungs  of  city  dwellers.  The  city  streets 
are  notoriously  dusty.  The  dust  consists  of  a  pulverized 
mass  of  refuse  in  which  building  sand,  ashes,  and  dry 
horse  manure  are  conspicuous  ingredients.  The  tendency 
of  this  dust  is  to  settle  to  the  earth,  but  excepting  imme- 
diately after  rain  or  snowstorms  it  never  is  absent  from 
the  air.  No  building  in  New  York  is  high  enough  to 
escape  it.  It  is  most  objectionable  in  the  crowded  streets. 
At  a  single  breath  a  pedestrian  may  take  into  his  nose  or 
mouth  a  much  greater  quantity  of  dust  than  the  average 
subway  employee  gets  in  a  month. 

Because  of  the  peculiarly  large  amount  of  iron  hi  the 
dust  of  the  subway,  the  disease  known  as  siderosis,  which 
exists  most  commonly  among  metal  polishers,  knife- 
grinders,  and  others  engaged  in  working  in  metal,  was 
given  special  attention. 

Disease  due  to  iron  dust.  The  inhalation  of  iron  dust 
produces  evil  effects  in  three  ways: 

1.  By  diminishing  the  respiratory  efficiency  of  the  lungs 
through  a  loss  in  their  elastic  property. 

2.  By  reducing  the  resistance  of  the  organs  to  invasion 
by  harmful  bacteria. 

3.  By  infecting  the  lungs  through  a  transportation  of 
disease  germs  to  places  favorable  for  their  inoculation. 

The  earliest  symptoms  of  siderosis  are  catarrh  and 
bronchitis,  but  shortness  of  breath  is  pronounced  by  all 
authorities  to  be  the  most  characteristic  symptom. 
Eventually  there  follows  what  appears  to  be  phthisis  with- 
out the  presence  of  tubercle  bacilli.  Yet  genuine  infective 
phthisis  is  the  most  common  cause  of  death. 

The  cause  of  the  unpleasant  symptoms  is  sometimes  not 
discovered  until  the  exposure  has  been  endured  for  years, 


206        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

depending  upon  the  amount  of  dust  in  the  air  and  the 
personal  resistance  to  it.  Even  in  fork-grinding,  among 
the  most  dangerous  of  dusty  occupations,  the  effects  may 
be  delayed  for  decades. 

Probably  a  great  many  men  engaged  in  dusty  occupations 
pass  their  lives  without  suspecting  the  cause  of  the  uncom- 
fortable symptoms  which  they  experience.  There  is  no 
doubt  that  large  numbers  die  from  infectious  pulmonary 
diseases  who  do  not  know  that  the  breathing  of  dusty  air 
has  led  to  their  infection. 

A  writer  in  a  recent  periodical  *  has  shown  the  start- 
lingly  high  rate  of  death  among  various  classes  of  metal 
workers  in  America  who  are  apparently  in  ignorance  of  the 
peculiar  danger  of  their  occupation. 

The  death  rate  among  steel  grinders  and  others  at 
Solingen,  Germany,  for  the  ten  years,  1885-95,  is  shown  in 
the  following  table,  in  which  the  number  of  deaths  from 
consumption  is  given  in  1000  deaths  from  all  causes  in 
Germany.2 


TABLE  XI 
DEATH   RATES    FROM   PHTHISIS  AT    SOLINGEN,    1885-1895 


Age. 

Grinders. 

All  males. 

14r-20 

25  8 

40  0 

21-30 

84  4 

69  9 

31-40 

75  9 

47  0 

41-50     .    .    . 

79.3 

36.0 

Over  50    

68.7 

25.8 

1  The   Independent,     "A   Story  of    the   Death   Claims."    Andrew 
Hellthaler.     December  27,  1906. 

2  Handbuch     der    Medizinischen     Statistik.     F.     Prinzing.     Jena, 
1906,  p.  489. 


HEALTH   OF  SUBWAY  EMPLOYEES  207 

DESCRIPTION  OF  THE  SUBWAY  EMPLOYEES 

Of  the  force  of  about  3000  men  employed  by  the  Inter- 
borough  Rapid  Transit  Company  to  operate  the  subway, 
about  800  were  motormen,  conductors,  or  guards  upon  the 
trains,  about  800  ticket  sellers,  ticket  takers,  or  porters  at 
the  stations,  and  about  1400  switchmen,  trackmen, 
mechanics,  painters,  engineers,  or  others  engaged  on  the 
road,  in  the  shops,  power  houses,  or  elsewhere.  This 
investigation  was  restricted  chiefly  to  the  uniformed  force, 
consisting  of  trainmen  and  station  men. 

All  who  occupied  responsible  positions  with  respect  to 
the  operation  of  the  trains  were  examined  physically  by 
the  company  before  they  were  employed,  records  being 
kept  of  their  age,  weight,  height,  respiratory  capacity, 
sight,  color  sense,  hearing,  and  heart  action. 

Absences  from  work  for  less  than  two  weeks  were  not, 
as  a  rule,  inquired  into  by  the  company,  but  in  the  event 
of  serious  sickness  the  men  were  examined  medically  before 
they  were  allowed  to  resume  their  work. 

In  this  investigation  the  employees  sent  by  the  company 
for  examination  were,  at  the  author's  request,  forty-five 
motormen,  forty-five  conductors,  and  ten  switchmen,  this 
list  including  employees  who  had  been  longest  on  the  road 
and  whose  work  had  kept  them  most  closely  under  con- 
ditions similar  to  those  experienced  by  the  traveling  public. 

Physical  appearance  of  the  men.  Nearly  all  the  men 
were  of  fine  physique.  Capacity  to  do  hard  manual  labor 
was  not  demanded  of  the  motormen,  nor  was  it  neces- 
sary that  the  conductors  should  have  more  than  ordinary 
strength ;  but  inasmuch  as  men  who  were  eligible  to  these 
grades  were  recruited  largely  among  persons  who  had  had 


208        THE  AIR  AND   VENTILATION  OF   SUBWAYS 

other  railroad  experience,  it  was  to  be  expected  that  the 
physical  standard  would  be  high. 

The  men  were  all  between  twenty-one  and  forty-seven 
years  of  age.  Their  average  height  was  5  feet  8i  inches, 
and  their  average  weight  169  pounds.  Their  general 
appearance  of  health  was  excellent  in  fifty-two  cases,  good 
in  thirty  cases  and  poor  in  only  two  cases. 

Sixty-nine  per  cent  of  the  men  claimed  to  be  citizens  of 
the  United  States.  About  half  were  city-bred. 

Regular  duties  of  the  men.  The  motormen  were  from 
the  regular  force  engaged  in  operating  the  trains.  Their 
employment  required  them  to  sit  in  a  small  compartment 
at  the  forward  end  of  the  car  at  the  head  of  a  train,  where 
they  operated  a  number  of  small  hand  levers.  The  position 
and  duties  of  these  men  prevented  them  from  doing  any  phys- 
ical work.  They  were  on  duty,  at  most,  ten  hours  each  day. 

The  conductors  serve  in  the  capacity  of  guards,  with 
some  additional  duties  and  responsibilities  not  of  interest 
in  this  investigation.  They  are  stationed  between  the  first 
and  second  cars  of  the  trains.  They  stand  while  at  work 
and  are  required  to  make  considerable  exertion  in  opening 
and  closing  the  heavy  doors  of  the  cars  at  the  stations.  In 
calling  out  the  names  of  the  stations  amid  the  noise  of  the 
moving  trains,  the  throats  of  the  conductors  are  put  to 
considerable  strain. 

The  duties  of  the  switchmen  require  them  to  couple  and 
uncouple  cars  and  switch  them  back  and  forth  from  one 
track  to  another  at  the  yards  and  storage  places.  This 
force  is  largely  composed  of  men  who  are  in  the  line  of 
promotion  to  motormen.  Of  the  ten  switchmen  examined 
four  had  been  accustomed  to  railroading  and  two  to  indoor 
work  exclusively. 


HEALTH   OF  SUBWAY  EMPLOYEES  209 

Medical  history  before  and  after  entering  subway  employ- 
ment. The  men  were  asked  to  give  histories  of  themselves 
before  and  after  entering  upon  their  subway  employment. 
In  some  cases  the  histories  given  were  undoubtedly  un- 
reliable, and  in  a  few  cases  the  men  were  evidently  dis- 
inclined to  talk;  but,  in  general,  their  attitude  was  one  of 
frankness  and  honest  cooperation,  and  it  seemed  safe  to 
put  considerable  reliance  upon  their  statements. 

Forty  per  cent  had  a  history  of  previous  serious  illness. 
Sickness  had  been  divided  proportionately  between  the 
three  classes.  The  longest  time  lost  through  illness  before 
going  to  work  in  the  subway  was  five  and  a  half  months. 

The  average  length  of  time  that  the  men  had  worked  in 
the  subway  up  to  the  time  of  examination  was  18.2  months. 
Only  two  men  had  been  employed  less  than  one  year;  these 
had  been  working  ten  months. 

Thirty  of  the  100  men  claimed  to  feel  in  better  condition 
at  the  time  of  examination  than  when  they  first  began 
to  work  in  the  subway;  five  felt  in  poorer  health;  sixty- 
five  were  unchanged.  In  fifty-four  cases  the  weight  had 
increased,  this  increase  varying  from  7f  pounds  to  15J 
pounds.  In  eighteen  cases  there  had  been  a  decrease. 

There  were  fifteen  cases  of  illness  reported  to  have 
occurred  during  the  period  of  subway  service.  Of  these 
only  nine  were  affections  of  the  respiratory  apparatus. 
There  had  been  three  cases  of  tonsilitis  and  one  case  of 
bronchitis.  In  twenty-seven  cases  time  had  been  lost  from 
illness,  but  most  of  these  illnesses  were  apparently  of  a 
trifling  character.  The  conductors  had  lost  more  time  than 
motormen  or  switchmen. 

Twenty-five  men  spoke  of  a  metallic  taste  in  the  mouth, 
although  this  point  was  not  mentioned  by  the  others.  In 
seventy-seven  cases  a  decided  and  peculiar  yellow  stain 


210        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

was  noted  on  the  clothing  where  it  was  moistened  by 
perspiration.  In  fifteen  cases  these  yellow  stains  were 
observable  on  the  body,  on  underclothing,  and  on  bed- 
clothes even  after  bathing.  Unusual  drowsiness  was 
mentioned  in  forty-six  of  the  fifty  cases  inquired  into. 

In  fifty-seven  cases  some  sort  of  precaution,  such  as 
douching,  was  taken  by  the  men  to  protect  the  nose  and 
throat.  In  seventeen  cases  the  nose  and  throat  were 
douched  every  day. 

RESULTS  OF  THE  PHYSICAL  EXAMINATIONS  OF  THE 
EMPLOYEES 

About  forty  minutes  were  consumed  in  examining  each 
man.  The  eyes,  nose,  and  throat  were  first  examined. 
The  men  were  then  required  to  strip  to  the  waist  and  an 
examination  was  made  of  the  organs  of  the  thoracic  and 
abdominal  cavity.  Measurements  of  the  chest  completed 
the  examination.  All  observations  and  verbal  information 
gathered  from  the  men  were  noted  in  blank  forms  prepared 
for  the  purpose. 

Examination  of  principal  organs  and  eyes.  In  nearly 
all  cases  the  principal  organs  were  in  good  condition.  The 
average  pulse  rate  was  eighty-five,  the  highest  104,  and  the 
lowest  fifty-six.  The  cervical  glands  were  enlarged  in 
sixteen  cases. 

The  eyes  were  found  to  be  slightly  red  or  irritated  in 
39  per  cent  of  the  men,  but  there  was  no  congestion  of 
the  ocular  conjunctiva.  These  conditions  were  no  more 
prevalent  in  one  class  than  in  another. 

Examination  of  the  upper  air  passages.  Abnormal  con- 
ditions found  in  the  nose  and  throat  differed  only  in  degree 


HEALTH  OF  SUBWAY  EMPLOYEES       211 

from  those  usually  found  in  dwellers  in  cities.  Bony 
irregularities  favor  catarrhal  conditions,  and  these  were 
probably  responsible  for  a  good  many  of  the  cases  of 
catarrh  noted  in  these  examinations. 

In  sixty-eight  cases  rhinitis  was  found.  It  was  marked 
in  two  conductors  and  two  motormen.  Bony  abnormali- 
ties of  the  nose  existed  in  forty-five  cases. 

Forty-three  of  the  men  gave  a  previous  history  of  catarrh. 
Fifty-four  had  catarrh  at  the  time  of  the  examination; 
twelve  of  these  men  considered  that  it  had  developed  in 
the  subway.  Catarrh  was  slightly  more  prevalent  among 
the  motormen  than  conductors. 

In  seventy-seven  cases  the  catarrhal  secretion  was 
black,  brown,  green,  or  dirty.  There  was  no  difference 
between  the  conductors,  motormen  and  switchmen  in  this 
particular.  It  was  described  as  from  the  throat  in  all  cases 
except  one.  In  this  exception  it  was  said  to  be  from  the 
stomach  —  an  obvious  impossibility. 

Pharyngitis  occurred  in  seventy-two  cases,  of  which 
fifty-three  were  acute  or  sub-acute.  There  was  about  as 
much  pharyngitis  among  the  motormen  as  among  the 
conductors. 

Laryngitis  occurred  in  eight  cases.  A  slight  congestion 
was  present  in  forty-seven  cases. 

Examination  of  the  lungs.  Cough  was  present  in  twenty- 
eight  cases.  In  only  one  case  was  it  considerable.  The 
chest  configuration  was  "  good  "  or  "  excellent  "  in  eighty 
cases.  It  was  "  poor  "  in  one  case.  The  average  circum- 
ference was  90.1  centimeters;  the  lowest  80  centimeters. 

Six  per  cent  of  the  men  gave  a  family  history  of  tuber- 
culosis. There  had  been  five  cases  of  bronchitis,  three  of 
which  occurred  among  the  conductors. 


212        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

Slight  emphysema,  antedating  the  beginning  of  subway 
employment,  occurred  in  two  cases,  both  among  conductors. 

In  thirteen  cases  slight  pains  were  described.  They 
were  usually  in  the  side  or  in  the  shoulder. 

Dry  pleurisy  was  present  in  fifty-three  cases.  It  was 
axillary  in  forty-four  cases;  bilateral  in  seventeen  cases;  at 
the  apex  in  twelve  cases.  It  was  distributed  proportion- 
ately among  the  three  classes  of  men  examined. 

Slight  infiltration  was  present  in  thirteen  cases.  It  was 
combined  with  pleurisy  in  eight  cases. 

There  were  five  cases  of  slight  fibrosis,  all  among  the 
motormen.  Three  of  these  cases  were  described  as  doubt- 
ful; they  were  combined  with  pleurisy. 

Of  all  these  conditions  the  prevalence  of  dry  pleurisy 
seemed  worthy  of  further  study. 

RESULTS  OF  ANALYSES  OF  SPUTUM,  URINE,  AND 
SWEAT 

Laboratory  tests  were  made  of  sputum,  urine,  and  sweat 
with  the  object  of  throwing  light  upon  the  findings  of  the 
medical  examinations. 

The  specimens  of  sputum  were,  in  every  case,  stained 
and  examined  microscopically  for  tubercle  bacilli.  None 
was  found.  The  presence  of  other  bacteria  and  macerated 
epithelium  from  the  mouth  was  frequently  noted,  but 
proved  nothing  of  importance. 

Specimens  of  sputum  were  examined  for  iron.  After 
some  experiment  with  different  methods,  the  test  adopted 
was  the  digestion  of  fresh  sputum  with  strong  hydrochloric 
acid  and  the  addition  of  ammonium  sulphocyanide.  Par- 
ticles of  iron  were  frequently  found,  but  it  was  impossible 
to  say  that  they  came  from  the  lungs.  In  fact,  in  prac- 
tically every  case  the  specimens  of  sputum  were  only 


HEALTH  OF  SUBWAY  EMPLOYEES       213 

secretions  from  the  mouth  and  throat.  Satisfactory 
specimens  from  the  bronchi  could  probably  only  be  obtained, 
if  at  all,  from  the  first  expectoration  of  the  early  morning. 
Such  specimens  were  requested  of  many  of  the  men,  but 
were  never  furnished. 

A  few  samples  of  urine  were  examined  for  iron.  The 
test  employed  was  the  same  as  that  used  in  examining 
sputum.  No  evidence  of  iron  was  discovered.  If  present 
at  all,  the  amount  was  extremely  slight. 

The  sweat  was  examined  for  iron  for  the  reason  that  the 
underclothing  of  many  of  the  employees  became  stained 
yellow  where  the  ordinary  marks  of  perspiration  might 
alone  be  expected.  The  color  of  these  stains  suggested 
iron.  Apparently  the  stains  came  from  iron  dust  dissolved 
upon  the  surface  of  the  body  and  were  not  due  to  the 
condition  of  the  sweat  which  was  exuded  from  the  skin. 
It  was  impossible  to  tell  from  the  tests  the  source  of  the 
iron,  but  the  fact  that  the  bodies  of  most  of  the  men  con- 
tained iron  particles,  and  the  fact  that  the  samples  of 
sweat  were  not  free  from  skin  dirt,  probably  offers  sufficient 
explanation  of  this  condition. 

RESULTS  OF  THE  AUTOPSIES 

Autopsies  were  performed  upon  the  bodies  of  five 
employees  and  one  other  person  killed  in  the  subway  during 
the  year  1906.  Four  of  the  employees  were  trackmen; 
one  had  been  employed  in  the  subway  six  months,  two  two 
months,  and  one  three  months.  In  addition,  there  were 
a  switchman  and  a  guard  who  had  been  employed  a  year 
each.  All  were  of  fine  physique  and  below  forty  years  of 
age.  Most  of  the  men  were  Italians  and  had  come  from 
Italy,  where  they  had  led  an  outdoor  life. 

The  autopsies  showed  but  few  of  the  conditions  which 


214        THE   AIR  AND   VENTILATION  OF   SUBWAYS 

have  been  described  in  medical  literature  as  characteristic 
of  siderosis  and  other  dust  diseases.  The  bodies  were 
usually  black  with  the  peculiar  dust  of  the  subway,  but  a 
surprisingly  small  amount  of  this  dust  was  found  within. 
Iron  particles  were  extremely  hard  to  find  in  the  trachea, 
bronchioles,  and  air  cells  of  the  lungs,  notwithstanding  the 
fact  that  the  men  had  been  run  over  and  had  probably 
gasped  dusty  air  directly  in  through  the  open  mouth  while 
expiring.  The  air  passages  were  invariably  in  a  normal 
condition  considering  the  fact  that  the  men  were  city 
dwellers. 

Under  the  microscope  and  with  proper  staining  methods 
the  lymphatics  were  seen  to  contain  metallic  iron,  but  not 
in  overwhelming  amount.  Particles  of  iron  could  now 
and  then  be  found  in  the  alveoli.  With  the  iron  particles 
were  masses  of  other  comminuted  foreign  matter,  chiefly 
soot.  The  lungs  had  lost  nothing  of  their  spongy  char- 
acter. There  were  no  bands  of  hard  fibrous  tissue  running 
through  them,  as  might  be  expected  in  siderosis.  The 
walls  of  the  bronchial  tubes  were  not  thickened. 

A  slight  diffuse  pleurisy  was  found  in  all  cases,  but  iron 
particles  did  not  exist  in  greater  amount  in  the  areas 
affected  by  this  pleurisy  than  elsewhere.  It  is  doubtful 
whether  any  of  these  pleurisies  could  have  been  discovered 
before  death. 

The  test  for  iron  was  a  refinement  of  the  familiar  hydro- 
chloric acid-and-potassium  ferrocyanide  method  performed 
upon  histological  sections.  The  iron  particles  were  also 
recovered  by  incineration. 

The  lungs  of  the  subway  employees  autopsied  contained 
somewhat  more  iron  than  a  lung  which  was  assumed  to  be 
normal,  but  this  normal  lung  contained  no  metallic  iron 
at  all.  Inasmuch  as  it  is  probable  that  the  lungs  of  all 


HEALTH  OF  SUBWAY  EMPLOYEES       215 

persons  who  have  lived  a  few  months  in  New  York  contain 
iron  particles  in  sufficient  number  to  be  detectable  by  the 
delicate  method  of  analysis  employed,  it  seems  likely  that 
the  standard  of  comparison  used  was  unreasonably  severe. 
It  may  be  said,  therefore,  that  the  autopsies  threw  no 
light  either  upon  the  possibly  evil  effects  of  the  dust  or  the 
prevalence  of  dry  pleurisy. 

It  would  be  equally  unfair  to  assume  from  this  analytical 
evidence  that  the  dust  was  or  was  not  injurious  when 
breathed  under  the  circumstances  which  surrounded  these 
men.  To  settle  this  question  would  require  many  more 
autopsies,  and  it  would  be  essential  to  have  them  performed 
upon  the  bodies  of  persons  who  have  been  longer  exposed 
to  the  air.  This  was,  of  course,  impossible  under  the 
circumstances. 

POSSIBLE  CAUSES  AND  CONSEQUENCES  OF  THE 
PLEURISY  FOUND 

The  fact  that  a  very  large  amount  of  pleurisy  existed 
among  the  subway  employees  had  not  been  anticipated. 
It  could  not  at  once  be  explained.  Its  importance  depended 
upon  whether  it  was  due  to  dust  or  other  condition  peculiar 
to  the  subway,  and  whether  it  was  associated  with  some 
physiological  condition  still  more  serious. 

It  became  desirable  to  inquire  very  carefully  into  the 
nature  of  the  pleurisy  and  the  conditions  with  which  it  was 
connected.  These  studies  were  too  extensive  to  be  fully 
reported  here,  but  it  seems  desirable  that  some  of  their 
more  essential  features  should  be  recorded. 

Pleurisy,  or  pleuritis,  as  it  is  more  accurately  called,  is 
an  inflammation,  or  the  result  of  an  inflammation,  of  the 
pleural  membrane  which  surrounds  the  lungs.  This  mem- 
brane has  been  likened  to  two  sacks,  which  are  partly  in 


216        THE  AIR  AND   VENTILATION   OF   SUBWAYS 

contact,  one  within  the  other.  The  inner  pleura  closely 
covers  the  lungs,  while  the  outer  lines  the  ribs  and  other 
tissues  of  the  chest  cavity.  In  health  the  surfaces  of  the 
two  pleura  are  very  smooth  and  glide  over  one  another 
without  perceptible  friction  as  the  lungs  expand  and  con- 
tract in  breathing.  In  pleurisy  this  smoothness  disappears 
and  inflammation  occurs.  Eventually  the  opposing  sur- 
faces become  rough  or  adherent,  a  condition  which  can  be 
detected  when  a  stethoscope  is  applied  to  the  outside  of  the 
chest  wall.  When  the  friction  sounds  are  very  pronounced, 
they  are  technically  described  as  friction  rubs,  and  when 
less  so,  crepitant  rales.  Other  terms  are  sometimes  used 
to  describe  the  sounds,  but  they  are  all  practically  some 
modification  of  these. 

Dry  pleurisy,  when  chronic,  is,  in  most  cases,  the  result 
of  the  more  common  acute  pleurisy  with  effusion,  yet  there 
is  a  primitive  dry  pleurisy  which  may  occur  without  any  of 
the  symptoms  which  generally  accompany  pleurisy  of  the 
latter  sort.  Pain  and  a  characteristic  cough  usually  call 
attention  to  the  existence  of  pleurisy.  It  was  a  remarkable 
fact,  repeatedly  noted  with  surprise  by  the  medical 
examiners,  that  the  subway  employees  rarely  complained  of 
pain,  cough,  or  any  other  of  the  clinical  symptoms  of  pleurisy. 

The  causes  of  pleurisy  are  believed  to  be  generally 
microbic.  Several  kinds  of  harmful  bacteria  have  been 
known  to  reach  the  pleura  and  set  up  inflammation.  It  is 
also  a  frequent  complication  in  pneumonia  and  bronchitis 
and  is  associated  to  some  extent  with  tuberculosis. 

The  frequency  with  which  pleurisy  is  noted  in  autopsy 
in  connection  with  other  diseases  of  the  respiratory  organs  is 
shown  in  Table  XII,  made  from  data  kindly  supplied  by 
Professor  F.  B.  Mallory,  Associate  Professor  of  Pathology, 
Harvard  Medical  School. 


HEALTH  OF  SUBWAY  EMPLOYEES 


217 


TABLE  XII 

FREQUENCY  WITH  WHICH  PLEURISY  WAS  FOUND  AT  AUTOPSY 
IN  1008  CASES  OF  OTHER  RESPIRATORY  DISEASES  AT  THE 
BOSTON  CITY  HOSPITAL,  1901-1905 


Number 

Number 
of  cases 

Number 
of  cases 

Number 

Number 

Number 
of  cases 

Number 
of  cases 

Year. 

of  autop- 
sies. 

of  lobar 
pneu- 
monia. 

of  bron- 
cho-pneu- 
monia. 

of  acute 
pleurisy. 

of  chronic 
pleurisy. 

of  tuber- 
culosis of 
lungs. 

of  tuber- 
culous 
pleurisy. 

1901 
1902 

177 
213 

32 
24 

37 
40 

34 

12 

110 
94 

44 
23 

1 

1903 

211 

23 

38 

30 

113 

46 

1 

1904 

200 

24 

72 

35 

117 

45 

1 

1905 

207 

27 

33 

29 

84 

19 

2 

Total 

1,008 

130 

220 

140 

518 

167 

5 

This  table  shows  that  pleurisy  existed,  with  other  respira- 
tory diseases,  to  the  extent  of  65.8  per  cent.  In  most  cases 
these  other  diseases  were  probably  the  inciting  cause  of  the 
pleurisy. 

In  a  way  not  yet  entirely  explained  a  sudden  chill  is  an 
important  factor  in  producing  pleurisy.  A  slight  dry 
pleurisy  may  follow  almost  immediately  upon  exposure. 
The  onset  may  resemble  the  onset  of  pleurisy  with  effusion, 
yet,  after  a  few  days,  the  symptoms  disappear  and  no 
effusion  occurs.  A  large  percentage  of  the  pleuritic  adhe- 
sions seen  after  death  are  believed  to  originate  in  this 
way. 

Dry  pleurisy  is  never  fatal.  Extensive  adhesions,  it 
appears,  may  somewhat  interfere  with  the  normal  action 
of  the  lungs,  but  if  they  do  so  their  effects  are  not  serious. 
The  importance  of  dry  pleurisy  depends  chiefly  upon  other 
diseases.  People  die  of  the  diseases  which  lead  to  the 


218        THE  AIR  AND   VENTILATION  OF  SUBWAYS 

pleurisy.  In  seeking  to  explain  the  condition  of  the  sub- 
way employees,  therefore,  it  seemed  desirable  to  look  care- 
fully for  respiratory  affections. 

Pleurisy  among  the  subway  employees.  For  purposes  of 
study,  the  records  of  the  cases  of  dry  pleurisy  among  the 
subway  employees  were  gathered  together  into  two  groups, 
according  to  the  friction  sounds  by  which  the  pleurisy  had 
been  diagnosed.  These  were  designated:  Group  I,  Pleu- 
ritic Crepitations,  and  Group  II,  Pleuritic  Rubs. 

Cases  of  dry  pleurisy  in  men  who  reported  that  they  had 
experienced  an  attack  of  pleurisy  or  pneumonia  before 
entering  the  subway  were  considered  sufficiently  accounted 
for  and  excluded  from  further  study.  This  reduced  the 
number  from  fifty-three  to  forty-five  cases.  Finally,  one 
case,  suspicious  of  a  former  attack  of  tuberculosis,  was 
excluded,  leaving  forty-four  cases  of  dry  pleurisy  unac- 
counted for. 

The  following  data  show  where  and  to  what  extent 
friction  sounds  were  heard  and  the  condition  of  the  nose 
and  throat  in  each  group: 

GROUP  I.    PLEURITIC  CREPITATIONS;   TWENTY-SEVEN  CASES. 

DISTINCTNESS  OF  CREPITATIONS.  LOCATION    OF    CREPITATIONS. 

Very  distinct 1        Apex 3 

Distinct 12        Axilla 20 

Slight 1£       Apex  and  axilla _4 

27  27 

With  these  the  following  conditions  of  the  nose  and 
throat  were  noted : 

RHINITIS.  PHARYNGITIS.                       LARYNGITIS. 

Marked  ....       2  Marked    ....       0  Marked  ....  1 

Present  ....       8        Present 1  Present  ....  10 

Slight     .    .    .    .     _7        Slight 13  Slight     .    .    .    .  11 

17  14  22 


HEALTH  OF  SUBWAY  EMPLOYEES       219 

The  foregoing  data  show  that  the  pleurisy  was  located 
mostly  in  the  axilla.  It  was  generally  accompanied  by 
pharyngitis  and  slight  laryngitis;  rhinitis  was  present  in 
about  half  the  cases  in  Group  I. 

GROUP  II.    PLEURITIC  RUBS;  SEVENTEEN  CASES. 

DISTINCTNESS    OF   RUBS.  LOCATION    OF   RUBS. 

Very  distinct 6  Apex 2 

Distinct 11  Right  axilla 5 

Slight     _0^  Left  axilla 10 

17  17 

The  following  conditions  of  the  nose  and  throat  were 
noted  in  these  cases: 

RHINITIS.  PHARYNGITIS.  LARYNGITIS. 

Marked  ....       2  Marked    ....  2  Marked      ...  0 

Present  ....       3  Present     ....  4  Present  ....  1 

Slight      .    .    .    .     U  Slight 10_  Slight     ....  11 

16  16  12 

It  will  be  observed  that  in  Group  II  the  pleurisy  was 
located  chiefly  in  the  axilla,  more  often  in  the  left  than  in 
the  right  side.  It  was  in  all  but  one  case  accompanied  by 
slight  rhinitis,  and  usually  by  pharyngitis  and  laryngitis. 

There  is  considerable  similarity  between  the  data  thus 
collated  for  the  two  groups.  The  friction  sounds  were 
found  in  the  axilla  as  a  rule.  In  more  than  half  the  cases 
there  was  congestion  or  inflammation  of  the  nose  and 
throat,  this  condition  being  very  slight  among  the  cases 
contained  in  Group  II,  in  which  the  pleurisy  was  most 
marked. 

A  rather  large  amount  of  congestion  and  inflammation 
of  the  nose  and  throat  existed  among  the  employees  who 
were  apparently  quite  free  from  pleurisy.  The  following 
data  illustrate  this  by  showing  the  frequency  with  which 


220        THE  AIR  AND   VENTILATION  OF  SUBWAYS 


laryngitis,  pharyngitis,  and  rhinitis  occurred  among  all  the 
employees  included  in  this  study : 


Num- 
ber of 
men. 

Employees. 

Rhinitis. 

Pharyngitis. 

Laryngitis. 

Cases. 

Per 

cent. 

Cases. 

Per 
cent. 

Cases. 

Per 
cent. 

47 
44 

Without  pleurisy  . 
With  pleurisy     .    . 

28 
34 

60 

77 

29 
34 

62 

77 

24 
21 

51 
47 

91 

Difference    .... 

6 

17 

5 

15 

3 

4 

These  studies  showed  that  the  condition  of  the  men  with 
and  without  pleurisy  was,  in  almost  all  ways,  identical, 
although  among  those  who  had  pleurisy  there  was  a  little 
more  rhinitis  and  pharyngitis  but  less  laryngitis  than  among 
those  who  were  without  it. 

Among  the  forty-four  cases  only  one  complained  of  sore 
throat,  although  seven  said  that  their  throats  became 
slightly  dry,  and  seven  complained  of  hoarseness.  In 
thirty-five  cases  the  men  spoke  of  a  slight  expectoration, 
thirty  describing  it  as  "  black,"  "  gray,"  "dark," 
"  dirty,"  or  "  green,"  and  three  "  white."  Pain  was 
mentioned  in  eight  cases.  It  was  always  described  as 
slight  or  occasional.  In  five  instances  the  pain  was  in  the 
shoulder,  or  axilla,  and  in  two  cases  in  the  chest. 

Normal  amount   of  pleurisy  among  city  dwellers.     In 
order  to  determine  just  how  excessive  was  the  prevalence 
of  dry  pleurisy  among  the  subway  employees,  it  seemed' 
desirable  to  inquire  how  often  this  disease  occurred  among 
persons  engaged  in  other  occupations. 


HEALTH  OF  SUBWAY  EMPLOYEES       221 

It  was  well  to  know  that  dry  pleurisy  in  its  milder  forms 
frequently  existed  among  persons  in  good  health  and  that 
it  was  extremely  rare  to  find  a  human  body  after  death  free 
from  a  roughened  or  adherent  pleura,  but  just  how  com- 
monly pleurisy  occurred  to  the  extent  noted  among  subway 
employees  could  not  be  determined  from  the  literature 
of  the  subject.  It  had  to  be  sought  by  special  investi- 
gation. 

Two  hundred  persons  were,  therefore,  subjected  to  a 
physical  examination  of  the  lungs  similar  to  that  given  the 
subway  employees.  The  work  was  done  by  the  same 
principal  examiner.  The  men  examined  represented  a 
large  number  of  vocations  and  were  chosen  at  random  from 
among  persons  admitted  to  Bellevue  Hospital  for  various 
causes. 

It  was  found  that  dry  pleurisy  existed  in  the  same 
degree  as  met  with  among  subway  employees  to  the  extent 
of  14J  per  cent.  If  allowance  had  been  made  for  their 
medical  histories,  deducting  old  pleurisies,  emphysema, 
and  pneumonia  from  the  count,  as  had  been  done  in 
studying  the  records  relating  to  the  subway  employees, 
this  percentage  undoubtedly  would  have  been  slightly 
reduced. 

Among  the  two  hundred  outsiders  the  pleuritic  sounds 
were  noted  in  the  axilla  in  twenty-two  cases  and  in  the 
apex  in  seven  cases.  This  was  about  the  same  ratio  as 
found  among  the  subway  employees.  The  diagnostic 
signs  noted  were  crepitant  rales  twenty-five  times  and 
friction  rubs  four  times.  Among  the  subway  employees 
the  occurrence  of  rubs  was  relatively  more  frequent;  in 
other  works,  the  pleurisy  was  more  marked. 

The  cases  of  dry  pleurisy  found  among  two  hundred  men 
engaged  in  various  employments  are  shown  in  Table  XIII. 


222        THE  AIR  AND   VENTILATION  OF  SUBWAYS 


TABLE  XIII 

OCCUPATIONS  OF  PERSONS  FOUND  TO  HAVE  DRY  PLEURISY 
AMONG  TWO  HUNDRED  PERSONS  TAKEN  AT  RANDOM 


Occupation. 

Cases  of 
pleurisy. 

Occupation. 

Cases  of 
pleurisy. 

Butcher     
Driver    
Laborer      
Iron  worker 

2 
3 
4 
2 

Street  cleaner    .... 
Conductor  
Real  estate  agent     .    . 
Janitor  

1 
1 
1 
1 

Steam  fitter     .    .    . 

1 

Poleman  

1 

Clerk  

1 

Gardener     

1 

Porter 

1 

Tunnel  worker 

1 

Brass  polisher      .    .    . 
Horse  clipper 

1 
2 

Laundryman  
Orderly 

1 
1 

Cook   .       ... 

1 

Oysterman  .... 

1 

Roofer    

1 

19 

10 

Of  these  twenty-nine  cases,  six  were  among  persons 
engaged  in  dusty  work. 

The  records  relating  to  the  forty-four  cases  of  pleurisy 
which  had  not  thus  far  been  explained  were  next  examined 
in  the  hope  of  determining  whether  a  knowledge  of  the 
previous  occupations  of  the  employees  would  throw  any 
light  upon  their  condition.  This  study  proved  more 
satisfactory  than  was  anticipated.  The  leading  facts  of 
interest  concerning  the  histories  of  the  men  are  given  in 
Table  XIV,  which  is  divided  into  two  parts  in  accordance 
with  the  severity  of  the  pleurisy  as  indicated  by  the  diag- 
nostic signs,  pleuritic  rubs,  and  pleuritic  crepitations. 

Of  the  seventeen  employees  in  whom  dry  pleurisy  was 
diagnosed  by  pleuritic  rubs,  six  had,  previous  to  their 
subway  employment,  been  steam  locomotive  engineers, 
firemen,  or  brakemen  on  outside  railroads,  with  an  average 
period  of  service  in  these  vocations  of  10.1  years  each.  Of 


HEALTH  OF  SUBWAY  EMPLOYEES 


223 


the  remaining  eleven,  six  had  been  motormen  or  conductors 
with  an  average  period  of  service  of  8.6  years.  Of  the 
remaining  five,  one  had  been  an  iron  worker  for  eighteen 
years. 

Of  the  twenty-seven  employees  whose  pleurisy  was 
diagnosed  by  pleuritic  crepitations,  nine  had  been  steam 
locomotive  engineers,  firemen,  or  brakemen,  with  an 
average  term  of  railway  service  of  7.4  years.  Of  the 
remaining  eighteen,  seven  had  been  motormen,  conductors, 
or  switchmen,  with  an  average  period  of  10.4  years. 


TABLE   XIV 

LENGTH  OF   SERVICE  IN  THE  SUBWAY  AND  IN   PREVIOUS  OCCU- 
PATIONS   OF    EMPLOYEES   WITH    PLEURISY 

PART  I.  —  Diagnostic  Sign  —  Pleuritic  Rubs 


No. 

Subway  employ- 
ment. 

Previous  employment. 

Grade. 

Period 
of  ser- 
vice. 

Occupation. 

Period 
of  ser- 
vice. 

1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 

Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Motorman 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 

Mo. 
20 
21 
19 
19 
15 
21 
21 
9 
22 
17 
22 
20 
16 
16 
16 
26 
16 

Locomotive  fireman      
Conductor     .    .       .    . 

Yrs. 
6 
11 
8 
5 
19 
14 
16 
10 
14 
6 
5 
8-9 
9 
8 
13* 
8 
17-18 

Locomotive  fireman  (5),motorman  (3) 
Motorman     

Storekeeper  
Locomotive  engineer 

Locomotive  fireman  (7),  engineer  (9) 
Motorman     
Locomotive  fireman  (9),  engineer  (5) 
Locomotive  fireman  (3),  brakeman  (3) 
Motorman 

Janitor 

Motorman 

Dry  goods                 .    .       .        .... 

Motorman  (1$),  furrier  (12)    .... 
Tamper 

Iron  worker 

224        THE  AIR  AND   VENTILATION  OF  SUBWAYS 


TABLE  XIV  —  Continued 

LENGTH  OF  SERVICE  IN  THE   SUBWAY  AND  IN  PREVIOUS  OCCU- 
PATIONS   OF    EMPLOYEES   WITH    PLEURISY 

PART  II.  —  Diagnostic  Sign  —  Pleuritic  Crepitations 


Subway  employ- 
ment. 

Previous  employment. 

No. 

Grade. 

Period 
of  ser- 
vice. 

Occupation. 

Period 
of  ser- 
vice. 

1 
2 
3 

4 

5 
6 

7 
8 

9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 

Motorman 
Motorman 
Motorman 

Motorman 

Motorman 
Motorman 
Motorman 
Motorman 

Motorman 

Motorman 
Motorman 
Switchman 
Switchman 
Switchman 
Switchman 
Switchman 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 
Conductor 

Mo. 
19 
19 
21 

15 

21 
9 
24 
10 

16 

22 
22 
22 
16 
15 
16 
16 
22 
19 
24 
16 
16 
16 
16 
16 
21 
16 
20 

Motorman 

Yrs. 
3 
10 

9 

19 
7 
16 
20 

22 

12 
18 
10 
10 
2 

5 
4 
7* 
5 
9 
19 
25 
12 
13 
7 
20 
6* 
12 

Conductor 

Locomotive      fireman      (3),      store- 
keeper (6)     

Locomotive  fireman  (3),  iron  molder 
(5),  steam  fitter  (11)      

Locomotive  fireman  (3),  brakeman  (4) 
Locomotive  fireman  (9),  engineer  (7) 
Motorman     .... 

Locomotive    fireman    (18),    motor- 
man  (4)  .    . 

Locomotive  fireman  (3),   brakeman 
(3),  conductor  (3),  yardmaster  (3) 
Switchman     .           , 

Brakeman     

Office  clerk  

Locomotive  fireman  

Expressman     

Conductor  (trolley)    
Clerk 

Elevator  man  

[nspector  (2),  bartender  (7)    .... 
Conductor  (5),  salesman  (14).    .    .    . 
Locomotive  fireman  (5),  railroads  (20) 
Machinist 

Conductor  (trolley) 

Leather  goods  . 

Clerk  (1),  contractor  (19)    

Rubber  goods  (1$),  truck  gardener  (5) 
Fireman  (2),  grocery  clerk  (10)     .    . 

Here  were  twenty-eight  men  who  had,  previous  to  their 
subway  work,  been  engaged  in  employments  in  which  they 


HEALTH  OF  SUBWAY  EMPLOYEES       225 

were  exposed  to  alternate  heat  and  cold  to  a  remarkable 
and  unusual  extent  and  for  an  average  period  of  nine  years 
each. 

Cause  of  the  pleurisy.  It  seemed  impossible  to  avoid 
the  conclusion  that  the  excessive  amount  of  dry  pleurisy 
was  largely  the  result  of  forgotten  or  unrecognized  attacks 
of  pleurisy  experienced  by  the  men  before  they  entered 
upon  their  subway  work. 

Many  circumstances  favored  this  opinion,  among  which 
may  be  mentioned  the  absence  of  pain  or  other  clinical 
symptoms  of  acute  pleurisy,  absence  of  pneumonia,  tuber- 
culosis, or  bronchitis,  and  the  excellent  health  records  of 
the  men  since  going  to  work  in  the  subway.  Further- 
more, there  was  as  much  pleurisy  among  the  motormen 
as  among  the  conductors,  while  their  exposure  both  to 
draughts  and  dust  was  quite  different:  the  motormen 
were  shut  up  in  their  small  compartments  and  were  well 
protected,  while  the  conductors  standing  between  the  cars 
were  much  exposed. 

Subtracting  the  twenty-eight  cases  of  pleurisy  thus 
explained  from  the  forty-four  cases  which  had  been  without 
explanation  left  sixteen  cases  finally  unaccounted  for.  This 
was  about  the  normal. 

CONCLUSIONS 

The  principal  conclusions  reached  by  the  author  con- 
cerning the  various  subjects  dealt  with  in  this  investiga- 
tion follow: 

1.  The  air  of  the  subway,  as  judged  by  analyses  and  by 
careful  studies  of  the  health  of  the  men,  was  not  injurious. 
If  injury  was  being  done,  the  subway  had  not  been  in 
operation  long  enough  and  the  investigation  had  been  too 
short  to  discover  it. 


226        THE   AIR  AND   VENTILATION  OF  SUBWAYS 

2.  The  most  objectionable  feature  of  the  air  was  the 
dust,  which  consisted  chiefly  of  angular  particles  of  iron. 
It  was  possible  also  that  injurious  bacteria  might  some- 
times be  associated  with  these  metallic  particles.    Lack  of 
strict  enforcement  of  the  city  ordinance  against  spitting 
and  the  want  of  skillful  care  in  cleaning  the  subway,  made 
this  danger  greater  than  it  need  be. 

3.  The  odor  and  heat  of  the  subway,  although  very  dis- 
agreeable,  were  not  actually   injurious  to   health.    The 
strong  draughts  and  changes  of  temperature  which  occurred 
at  the  stations  were  the  most  objectionable  atmospheric 
conditions,  so  far  as  health  was  concerned. 

4.  The  employees  submitted  by  the  company  for  physical 
examination  were  a  particularly  robust  lot  of  men.    From 
their  excellent  physique  it  appeared  that  they  had  been 
carefully  selected,  a  fact  which  was  explained  when  it  was 
found  that  a  large  majority  of  the  men  had  previously  been 
engaged  in  railroading,  where  capacity  to  do  hard,  manual 
labor  was   required.    It    was   fair   to   assume   that   the 
employees  examined  represented  a  fair  average  of  all  those 
who  came  in  close  contact  with  the  passengers,  so  far  as 
resistance  to  disease  was  concerned. 

5.  There   had    been   very   little   sickness   among   the 
employees  during  their  period  of  subway  employment, 
judging  by  the  accounts  which  the  men  gave.     No  informa- 
tion with  respect  to  this  matter  was  obtainable  from  the 
operating  company.     Many  of  the  men  claimed  to  have 
gained  weight  since  they  had  been  working  in  the  subway 
—  a  fact  due,  apparently,  less  to  any  peculiarly  healthful 
property  of  the  air  than  to  the  easier  work  required. 

6.  Most  of  the  men  spoke  of  drowsiness.    This  was 
perhaps  to  be  explained  by  the  comparative  darkness  of 
the  subway,  the  monotony  of  the  work,  and  fatigue  of  the 


HEALTH  OF  SUBWAY  EMPLOYEES       227 

eyes.    The  drowsiness  was  apparently  never  sufficient  to 
keep  the  men  from  performing  their  duties  properly. 

7.  A  large  number  of  employees  complained  of  yellow 
stains  which  came  upon  their  underclothing,  as  they  sup- 
posed, from  their  sweat.    This  caused  considerable  incon- 
venience.   The  stains  probably  resulted  from  iron  particles 
upon  the  body  which  were  acted  upon  by  the  sweat.     Inves- 
tigation excluded  the  possibility  that  the  sweat  itself  was 
discolored. 

8.  Careful    physical    examinations    showed    that    an 
excessive  amount  of  dry  pleurisy,  without  pain  or  other 
physical  discomfort,   existed  among  the  men.     Pleurisy 
occurred  to  the  extent  of  53  per  cent  among  the  employees 
and  to  the  extent  of  14  J  per  cent  among  persons  not  engaged 
in  subway  work. 

The  cause  of  the  dry  pleurisy  was  not  at  first  apparent, 
but  upon  investigation  it  appeared  to  have  been  in  no  way 
due  to  the  subway.  Nine  per  cent  of  the  men  had  medical 
histories  which  accounted  for  their  condition,  and  28  per 
cent  had  worked  for  many  years  under  conditions  known 
to  be  favorable  to  the  occurrence  of  this  disease.  The 
pleurisy  had  no  visible  effect  upon  the  health  of  the  men 
and  was  not  likely  to  be  injurious  to  them  in  the  future. 

9.  Congestion  and  inflammation  of  the  upper  air  passages 
were   prevalent.     Rhinitis   and    pharyngitis   in   acute   or 
chronic  form  occurred  in  about  70  per  cent  of  the  men 
examined.     Laryngitis    was    less    common,    occurring   in 
about  55  per  cent.    These  figures  are  somewhat  above  the 
normal,   considering  the  degree  of  severity  represented. 
No  case  of  bronchitis  was  discovered.     The  prevalence  of 
the  minor  respiratory  affections  noted  was  due,  apparently, 
more  to  the  previous  employments  of  the  men  than  to  their 
present  surroundings,  although  the  excessive  use  of  the 


228        THE   AIR  AND   VENTILATION   OF   SUBWAYS 

voice  required  of  the  conductors  seemed  likely  to  aggravate 
these  affections. 

10.  Analyses  of  the  sputum,  urine,  and  sweat  of  the  men 
showed  that  iron  dust  was  given  off  only  in  the  sputum. 
This  sputum  was  derived  mostly  from  the  mouth  and 
throat,  where  most  of  the  iron  particles  drawn  in  with  the 
inspired  air  were  caught. 

11.  The  findings  at  autopsy  threw  no  light  upon  the 
possibly  evil  effects  of  the  dust.     The  men  whose  bodies 
were  examined  had  worked  too  short  a  time  in  the  subway 
for  information  of  value  in  this  direction  to  be  obtainable. 
Iron  was  found  in  the  lungs  of  all,  but  to  an  extent  which 
had  produced  no  evil  consequences. 

RECOMMENDATIONS 

Certain  specific  recommendations  seemed  to  be  required, 
under  the  circumstances. 

1.  Care  should  be  taken  that  persons  employed  in  the 
subway  are  free  from  respiratory  disease  or  a  tendency 
toward  it.     This  rule  should  be  extended  to  all  grades  and 
positions  and  made  to  apply,  also,  to  the  women  who 
operate  the  news  stands. 

2.  Thorough   physical   examinations,   especially  of  the 
respiratory  apparatus  and  heart,  should  be  made  of  all 
employees   when   they  are  first   engaged  and   at  yearly 
intervals  subsequently. 

3.  While  the  dust  was  not  proved  to  have  produced 
harmful   results,    sanitary   considerations  require  that  it 
should  be  prevented  as  far  as  practicable  from  getting  into 
the  air.     To  this  end  (a)  sand  and  sawdust  should  not 
purposely  be  scattered  on  the  stairways  and  platforms; 
(6)  sweeping  and  cleaning  should  be  done  in  a  strictly 
sanitary  manner,  preferably  in  accordance  with  the  recom- 


HEALTH  OF  SUBWAY  EMPLOYEES       229 

mendations  of  the  Advisory  Board  of  the  Department  of 
Health;  and  (c)  investigations  should  be  made  to  deter- 
mine whether  it  is  feasible  to  prevent  or  collect  much  of 
the  iron  dust. 

4.  The  city  ordinance  against  spitting  should  be  enforced 
to  the  letter.  Although  some  progress  has  already  been 
made  in  preventing  it,  spitting  is  still  practiced  occasionally 
on  the  platforms  and  on  the  roadbed.  Not  only  passengers, 
but  employees  are  offenders  in  this  direction. 


INDEX 


PAGE 

Adjuncts  of  subways 7 

Air  of  confined  spaces 32-47 

of  cities  and  towns 25-32 

gases .;,;••••• •  •  ••  • 2G 

of  European  subways 72-98 

of  London 24 

of  New  York 25 

of  Paris ....'...  25 

of  the  Central  London  Railway 80 

of  the  City  and  South  London   Railway •. 83 

of  the  Metropolitan  and  District  Railway  of  London 72 

of  the  Metropolitan  Railway  of  Paris 84 

of  the  New  York  subway   -. 99-193 

currents  in  the  New  York  subway 116 

required  by  human  beings 41 

valves  in  the  New  York  subway 120 

Analyses  for  bacteria  in  the  New  York  subway: 

filter  method. *M;.  -V. . . '.. 158 

plate  method .'•'.^•'v--. -.'  •  • ;  • 156 

for  carbon  dioxide  in  the  New  York  subway 139 

for  oxygen  in  the  New  York  subway 146 

of  air  of  the  Metropolitan  and  District  Railway  of  London ....  75 
of  sputum,  urine  and  sweat  of  employees  in  the  New  York  sub- 
way   . ,••••••  ••-.. 212 

Anemometer  observations  in  the  New  York  subway 117 

Apparatus  for  bacterial  analyses  in  the  New  York  subway,  159, 160, 162 

for  carbon  dioxide  analyses  in  New  York  subway 139 

for  dust  examinations  in  the  New  York  subway 180 

for  humidity  observations  in  the  New  York  subway 124 

for  oxygen  analyses  iri^the  New  York  subway 146 

for  recording  temperature  in  the  New  York  subway: 

psychrometer 124 

thermograph 127 

for  removing  dust  in  the  Central  London  tube 96 

231 


232  INDEX 

PAGE 

Atmospheric  impurities  in  cities . 29 

Effects  on  plants,  metals  and  stone 29 

health 31 

Atmosphere  of  the  open  country 12-23 

bacteria 22 

carbon  dioxide 17 

composition 14 

dust 20 

forms  of  life 22 

moisture,  cold  and  heat 19 

odors ;s 15 

oxygen 12 

ozone 15 

peroxide  of  hydrogen 15 

water  vapor 18 

Autopsies  on  employees  in  the  New  York  subway 196,  213-215 

Bacteria  in  city  air 29 

in  normal  air 22 

classes 23 

destructive  conditions 23 

in  the  air  of  the  New  York  subway 166,  191,  198 

effects  on  oil 169 

sweeping 168 

trains 168 

wind 166 

number 164 

origin 166 

in  the  air  of  the  City  and  South  London  Railway 83 

in  the  air  of  the  Central  London  Railway 82 

in  the  dust  of  the  New  York  subway 163,  170,  188, 198,  201 

Bacterial  condition  of  the  air  of  the  New  York  subway 154-170 

examination  of  dust  in  the  New  York  subway 178 

methods  of  analyses  in  the  New  York  subway: 

filter 158 

plate 156 

Baker  St.  and  Waterloo  Railway 3 

Bearings  of  subways  on  health 11 

Berlin  subway 4 

temperature 94 

ventilation 98 

Blackwall  tunnel 2 

Blow  holes . .  62 


INDEX  233 

PAGE 

Blow  holes  in  the  Metropolitan  Railway  of  Paris 89 

in  the  New  York  subway 113, 120 

Boston  subway 6 

fans 56 

ventilation 58 

Brake  block  on  London  roads 97 

Brake  shoes  in  the  New  York  subway  as  a  cause  of  dust 186 

Bronchitis  among  employees  in  the  New  York  subway 211 

Budapest  subway 5 

Calculation  of  fresh  air  requirements 44 

Calculations  for  ventilating  enclosed  spaces  51 

Carbon  dioxide  analyses 36 

in  the  New  York  subway 139 

Carbon  dioxide  results  in  the  New  York  Subway: 

amount 147 

at  express  and  local  stations 152 

below  and  above  50th  St 153 

between  stations 152 

different  elevations 154 

hourly  variations 148 

seasonal  variations 148 

in  the  air  of  Glasgow i 24 

in  the  air  of  Manchester 24 

in  the  air  of  Perth 24 

in  normal  air 17 

in  London  air 24 

in  New  York  City  air 26 

in  Paris  air 25 

in  air  of  the  Central  London  Railway 81 

in  the  air  of  the  City  and  South  London  Railway 83 

in  the  air  of  the  Metropolitan  Railway  of  Paris 87 

in  the  air  of  the  New  York  subway 190, 196 

produced  by  human  beings 35 

Carbonic  acid  in  the  air  of  the  Metropolitan  and  District  Railway 

of  London 76 

Carbon  dioxide  in  the  air  of  the  Metropolitan  and  District  Rail- 
way of  London 76 

Cars  in  European  subways 92 

Catarrh  among  employees  in  the  New  York  subway 211 

Causes  of  dust  in  the  New  York  subway: 

brake  shoes 186, 198 

other  substances 185,  199 


234  INDEX 

PAGE 
Causes  of  odor  in  the  New  York  subway: 

cement 175 

concrete 176 

disinfectants 175 

fuses 175 

hot  boxes 175 

human  beings 176 

motors 174 

tobacco  smoke 175 

Cause  of  heating  in  European  subways 94 

Causes  of  pleurisy 216 

Cement  as  a  cause  of  odor  in  the  New  York  subway 175 

Central  London  Railway 3,  80-83 

Bacteria  in  the  air 82 

Carbon  dioxide  in  the  air 81 

Construction v 80 

Dust  removing  apparatus ^ 96 

Fans 61 

Health  of  employees , 98 

Ventilation 61,  80 

Changes  in  ventilating  arrangements  of  the  New  York  sub- 
way           120 

Character  of  dust  in  the  New  York  sutiway 183 

Characteristics  of  good  and  bad  air 12-47 

Charing  Cross,  Euston  and  Hampstead  Railway 3 

Chemical  condition  of  air  of  the  New  York  subway 139-154 

Chemical  composition  of  dust  in  the  New  York  subway,    186,  197,  201 

Chemical  examination  of  dust  in  the  New  York  subway 178 

Circulation  of  air  in  the  New  York  subway 118 

City  air: 

bacteria 29 

dust 28 

gases 26 

City  and  South  London  Railway 3,  83-84 

bacteria  in  the  air 83 

carbon  dioxide  in  the  air 83 

City  dusts: 

composition 28 

Cleanliness  of  European  subways 92 

of  the  New  York  subway 110 

Coal  consumed  in  New  York 26 

Coal  soot  in  London,  Manchester  and  Glasgow 31 

Composition  of  city  dusts 28 


INDEX  235 

PAGE 

Composition  of  pure  atmospheric  air 14 

of  New  York  subway  dust 185 

of  respired  air 32 

Conclusions  of  investigation  of  air  of  New  York  subway  ....      189-193 
of  investigation   into   the  health  of  New   York  subway  em- 
ployees       225-228 

Condition  of  the  air  of  the  Metropolitan  and  District  Railway  of 

London 75 

of  the  air  of  the  New  York  subway 196-206 

bacterial 154-170 

chemical 139-154 

Concrete  as  a  cause  of  odor  in  the  New  York  subway 176 

Conductors  in  the  New  York  subway 208 

Congestion 9 

effects  of  subways 9 

effects  upon  convenience  of  public 10 

conduct  of  trade 10 

studies  in  America  and  Europe 10 

Construction  of  Central  London  Railway 80 

of  the  Metropolitan  Railway  of  Paris 84 

of  the  New  York  subway 102 

Contributing  factors  to  diseases  from  dust 202 

Currents  of  air  in  the  New  York  subway 116 

Dangers  of  dust  in  the  New  York  subway 201 

Defenses  against  dust 203 

Description  of  employees  in  the  New  York  subway 207-210 

Dew  point 19 

Diffusion  of  air  in  the  New  York  subway 191 

Diseases  among  city  people: 

Respiratory 204 

due  to  infected  air 32 

due  to  poor  ventilation 46 

Disease  from  dust: 

Contributing  factors 202 

Iron  dust 205 

Disinfectants  in  European  subways 93 

in  the  New  York  subway 164,  170, 175 

Dryness  of  European  subways 94 

of  the  New  York  subway 109 

Dust  in  city  air 28 

in  European  subways 96 

in  normal  atmosphere 20 


236  INDEX 

PAGE 

Dust  —  continued: 

Composition  in  country  air 20 

Composition  in  sea  air 20 

As  an  ingredient  of  the  atmosphere 21 

Aitken's  studies  21 

in  the  air  of  the  Metropolitan  Railway  of  Paris 88 

in  the  New  York  subway 177-188 

Composition 185 

Dangers 201 

Defenses 203. 

Injurious  properties 201 

Iron 183,  197 

Mechanical  composition 185 

Metallic 186 

Methods  of  examination 178 

Microscopical  examination 178,  183,197 

Origin  of  metallic  dust 186 

Physical  character 183 

Physical  composition 197 

Sources  of  iron  dust 198 

Variations  in  amount 188 

Weight 178,  186,  200 

Weight  inhaled  by  passengers 181,  200 

Bacterial  examination 178 

Chemical  examination 178 

removing  apparatus  in  the  Central  London  tube 96 

Duties  of  employees  in  the  New  York  subway 208 

Effect  of  odors  on  passengers  in  the  New  York  subway 170 

of  oil  on  bacteria  in  the  New  York  subway 169 

of  sweeping  on  bacteria  in  the  New  York  subway 168 

of  trains  on  bacteria  in  the  New  York  subway 168 

of  wind  on  bacteria  in  New  York  subway  and  streets 166 

Effects  of  atmospheric  impurities  in  cities 29 

of  bad  ventilation 45 

of  subways  on  congestion  of  population 9 

Electric  traction  in  relation  to  subways 7 

Employees  in  the  New  York  subway: 

Autopsies 196,  213-215. 

Bronchitis 211 

Catarrh 211 

Conductors 208 

Description 207,  210 


INDEX  237 

PAGE 

Employees  in  the  New  York  subway  —  continued: 

Duties 208 

Examination 210-211 

Medical  history 209 

Motormen 208 

Pharyngitis 211,  220 

Physical  appearance 207 

Physical  examination 195,  216 

Plans  of  investigation  into  health 195 

Rhinitis 211,  220 

Sputum 212 

Sweat 213 

Switchmen 208 

Tuberculosis 211 

Urine 213 

Essentials  of  construction  and  operation  at  the  time  of   the   investi- 
gation into  the  air  of  the  New  York  subway 102-123 

European  subways: 

Disinfectants 93 

Dryness 94 

Dust 96 

Inspections 90 

Molds 97 

Odors 93 

Roadbeds 92 

Temperature 93 

Evolution  of  modern  subway 1-10 

Examination  of  dust  in  the  New  York  subway: 

Bacterial 178 

Chemical 178 

Methods 178 

Microscopical 178,  183, 197 

Exhaust  and  plenum  principles  of  ventilation 54 

Expired  air 35 

Express  and  local  stations  in  the  New  York  subway: 

carbon  dioxide 152 

Fans  for  assisting  ventilation 55 

in  Central  London  Underground 61 

in  Boston  subway 56 

in  the  newest  London  tubes 60 

in  the  New  York  subway 121 

in  the  Severn  and  Mersey  tunnels 58 


238  INDEX 

PAGE 

Filter  method  of  bacterial  analysis  in  the  New  York  subway 158 

Floor  of  the  New  York  subway 103 

Formulae  for  ventilation 51 

Forms  of  life  in  normal  air 22 

Fundamental  considerations  in  ventilating  subways 48-54 

Fuses  as  a  cause  of  odor  in  the  New  York  subway 175 

Gases  in  air  of  cities  and  towns 26 

Coal 26 

industrial  origin 26,  27 

injury  to  health 28 

of  normal  atmosphere 14 

Glasgow  subway 5 

Great  Northern  and  City  Railway 3 

Great  Northern,  Piccadilly  and  Brompton  Railway 3 

Health  of  Employees  in  the  Central  London  Railway 98 

on  the  London  Underground  Electric  Railways 98 

on  the  Metropolitan  and  District  Railway  of  London 77 

in  the  New  York  subway ; 194-229 

in  the  Paris  subway 98 

Heating  of  subways 53 

in  European  subways: 

cause 94 

Heat  produced  by  human  beings 37 

Hot  boxes  as  a  cause  of  odor  in  the  New  York  subway 175 

Hourly  variations  in  carbon  dioxide  in  the  New  York  subway.  .  .  148 

Humidity . 19 

in  New  York  subway 135 

Impurities  of  the  atmosphere  of  cities 29 

Infected  air: 

diseases ; 32 

Injurious  properties  of  dust  in  the  New  York  subway 201 

Inspections  of  European  subways 90-98 

Investigation  of  the  air  of  the  Metropolitan  and  District  Railway 

of  London 72 

of  the  air  of  the  City  and  South  London  Railway 83 

of  the  air  of  the  Central  London  Railway 81 

of  the  air  of  the  New  York  subway 99  * 

of  the  air  of  the  New  York  subway  by  Dr.  Charles  F.  Chandler ...  99 

Iron  in  dust  in  the  New  York  subway 183,197 

diseases . .  205 


INDEX  239 

PAGE 

Iron  dust,  sources 198 

in  lungs  of  employees  in  New  York  subway 214 

Koniscope 181 

Laryngitis  among  employees  in  the  New  York  subway 211,  220 

Lighting  of  the  New  York  subway 109 

Local  and  express  stations  in  the  New  York  subway: 

carbon  dioxide 152 

London  air 24 

London  tubes 3 

fans 60 

temperature 94 

ventilation 60,  87 

London  underground  electric  railways: 

health  of  employees 98 

Louvres  in  the  New  York  subway 120 

Lubricants  in  the  New  York  subway 173 

Lungs  and  throats  of  city  dwellers 204 

Lungs  of  employees  in  the  New  York  subway: 

iron 214 

Mechanical  composition  of  dust  in  the  New  York  subway 202 

principles  involved  in  ventilation 50 

Medical  history  of  employees  in  the  New  York  subway 209 

Mersey  tunnel 58 

Metallic  dust  in  the  New  York  subway 186 

Methods  of  bacterial  analyses  in  the  New  York  Subway 155 

filter 158 

plate 156 

of  dust  examinations  in  the  New  York  subway 178 

of  investigating  odors  in  the  New  York  subway 172 

of  temperature  observations  in  the  New  York  subway 123 

of  ventilating  subways 48-71 

Metropolitan  and  District  Railway  of  London 3,  72-79 

condition  of  the  air 75 

health  of  employees 77 

methods  of  ventilation 77 

natural  ventilation 75 

operating  conditions 73 

ventilation  experiments 74 

Metropolitan  Railway  of  Paris; 

blow  holes 89 

carbon  dioxide . .  89 


240  INDEX 

PAGE 
Metropolitan  Railway  of  Paris  —  continued: 

construction 84 

dust 88 

health  of  employees 98 

natural  ventilation 75 

odor 90 

operation 84 

passengers  carried 85 

stations 84 

temperature 88 

ventilation 85 

Microscopical  examination  of  dust  in  the  New  York  subway,  178,  183,  197 

Moisture  in  atmosphere 19 

produced  by  human  beings 38 

Molds  in  European  subways 97 

in  the  New  York  subway 163,  166 

Motormen  in  the  New  York  subway 208 

Motors  as  a  cause  of  odor  in  the  New  York  subway  174 

Movements  of  trains  in  the  New  York  subway 115,  190 

New  York  City  air 25 

carbon  dioxide 26 

Natural  ventilation  of  subways 62 

on  the  Metropolitan  and  District  Railway  of  London 75 

Normal  air: 

bacteria 22 

carbon  dioxide 17 

dust 20 

forms  of  life 22 

gases 14 

odors 15 

oxygen 12 

water  vapor 18 

Number  of  bacteria  in  New  York  subway  and  streets 164 

Observations  with  anemometers  in  the  New  York  subway 117 

Odor  in  the  air  of  the  Metropolitan  Railway  of  Paris 90 

Odors  in  air  of  confined  spaces 34 

in  European  subways 93 

in  normal  air 15 

in  the  New  York  subway 170-176 

cement 175 

concrete .  .  176 


INDEX  241 

PAGE 
Odors  in  the  New  York  subway  —  continued: 

disinfectants 175 

fuses 175 

hot  boxes 175 

methods  of  investigating 172 

motors 174 

odors  of  human  origin 176 

tobacco  smoke 175 

effect  on  passengers 170 

Oil  in  the  New  York  subway 163,  173 

effects  on  bacteria 169 

Opening  of  New  York  subway 99 

Operating  conditions  on  the  Metropolitan  and  District  Railway  of 

London 73 

Operation  of  the  Metropolitan  Railway  of  Paris 84 

of  New  York  subway 104 

Origin  of  bacteria  in  New  York  subway 166 

of  metallic  dust  in  the  New  York  subway 186 

Oxygen  in  normal  air 12 

reserve  supply  in  air 13 

decrease  in  supply  over  the  earth 13 

in  the  air  of  the  Metropolitan  and  District  Railway  of  London,  76 

in  the  New  York  subway 146, 154, 190, 196 

Ozone  in  the  atmosphere 15 

Paris  air 25 

subways 4, 84 

Passengers  in  the  New  York  subway: 

effects  of  odors . 170 

number  carried 108, 115 

weight  of  dust  inhaled 187,  200 

Peroxide  of  hydrogen  in  the  atmosphere 15 

Pharyngitis  among  employees  in  the  New  York  subway.  ...     211,  220 

Phenomena  of  ventilation  in  the  New  York  subway 115 

Physical  appearance  of  employees  in  the  New  York  subway 207 

character  of  dust  in  the  New  York  subway 183 

composition  of  dust  in  the  New  York  subway 197 

examination  of  employees  in  the  New  York  subway 195,  210 

principal  organs 210 

eyes 210 

nose 210 

throat 210 

lungs 211 


2i2  INDEX 

PAGE 

Physical  principles  involved  in  ventilation 49 

Piston  action  of  trains 64, 97 

Berlin  Zossen  tests 65 

observations  in  Paris 65 

observations  in  New  York 65 

Plan  of  investigation  into  health  of  employees  in  the  New  York 

subway 195-196 

Plate  method  of  bacterial  analysis  in  the  New  York  subway.  .  .  .  156 
Pleurisy : 

among  city  dwellers 220 

among  New  York  subway  employees 212,  215,  225 

causes 216 

Pneumococcus  tests  in  the  New  York  subway 162,  169,  198 

Practical  systems  in  use  in  ventilating  subways 54-71 

Provisions  for  ventilating  the  New  York  subway 113 

changes  in  the  ventilating  arrangements 120 

Psychrometer 124 

Questions  investigated  in  relation  to  the  air  of  the  New  York 

subway 100 

Recommendations  in  regard  to  the  New  York  subway 228 

Renewal  of  air  in  the  New  York  subway 190, 196 

Representative  section  of  New  York  subway 104 

Respiration 12 

Respiratory  diseases  among  city  people 204 

Respired  air 32 

Results  of  carbon  dioxide  analyses  in  the  New  York  subway 147 

of  bacterial  analyses  in  the  New  York  subway ; 164 

of  dust  examinations  in  the  New  York  subway 183 

of  odor  investigations  in  the  New  York  subway 172 

of  physical  examinations  of  employees  in  the  New  York  sub- 
way    210-212 

Rhinitis  among  employees  in  the  New  York  subway 211,  220 

Roadbed  of  the  New  York  subway 1 10 

Roadbeds  of  European  subways 92 

Route  of  the  New  York  subway 106 

Sanitary  features  of  construction  in  the  New  York  subway ....  109 
Scope  of  the  investigation  into  the  air  of  the  New  York  subway,  100-102 
Seasonal  variations  in  carbon  dioxide  in  the  New  York  subway,  148 

Sea  air 20 

Sensible  condition  of  the  air  of  European  subways 90 


INDEX  243 

PAGE 

Severn  tunnel 58 

Skill  in  design  and  maintenance  of  subways 49 

Smoke  in  the  air  of  towns  and  cities 27, 29 

Sources  of  iron  dust  in  the  New  York  subway 198 

Space  required  by  human  beings 39 

Spitting  in  European  subways 92 

in  the  New  York  subway 198 

Sputum  of  employees  in  the  New  York  subway 212 

Stairways  of  the  New  York  subway 114 

Standards  of  living  elevated  through  education 41 

of  purity  for  the  air  of  schools  and  factories 44 

of  purity  for  subway  air 42 

Stations  of  the  New  York  subway 110,  133 

Steel  and  concrete  in  the  New  York  subway 103 

Stone  ballast  in  the  New  York  subway 172 

Sulphurous   acid  in    the  air  of  the    Metropolitan   and  District 

Railway  of  London 77 

Subways: 

Berlin 4 

Boston 5 

Budapest 5 

Central  London : 3 

Charing  Cross,  Euston  and  Hampstead 3 

City  and  South  London 3 

Great  Northern  and  City 3 

Great  Northern,  Piccadilly  and  Brompton 3 

Glasgow 5 

London 1,2 

Metropolitan  and  District 3 

New  York 5 

Paris 4 

Waterloo  and  City 3 

Subways  and  the  public  health 1-11 

Supply  of  air  required 41 

Sweat  of  employees  in  the  New  York  subway 213 

Switchmen  in  the  New  York  subway 208 

Temperature  in  European  subways 93 

and  humidity  in  the  New  York  subway 123-138, 189 

at  stations 133 

before  opening 129 

immediately  after  opening 131 

in  the  summer  of  1905 .  .  .  131 


244  INDEX 

PAGE 
Temperature  in  European  subways  —  continued  : 

methods  of  observation 123 

in  the  air  of  the  Metropolitan  Railway  of  Paris 88 

in  the  Berlin  subway 94 

in  the  London  tubes 94 

Thermograph 127 

Throat  and  lungs  of  city  dwellers 204 

Ticket  sales  in  the  New  York  subway 107 

Tobacco  smoke  as  a  cause  of  odor  in   the  New  York  subway.  .  . .  175 

Toilet  rooms  in  the  New  York  subway Ill 

Track  of  the  New  York  subway 7, 112 

Train  movements  in  the  New  York  subway 115,  190 

Travel  in  the  New  York  subway 106 

Tuberculosis  among  employees  in  the  New  York  subway 211 

Urine  of  employees  in  the  New  York  subway 213 

Ventilation 45 

experiments    on   the   Metropolitan   and    District    Railway    of 

London 74,  77 

of  subways: 

difference  in  subways,  tunnels  and  mines 48 

skill  in  design  and  maintenance 49 

physical  principles 49 

mechanical  principles 50 

practical  systems  in  use 54 

of  Berlin  subway 98 

of  Boston  subway 56 

of  the  Central  London  Underground  Railway 61,  80 

of  the  Metropolitan  Railway  of  Paris 85 

of  the  New  York  subway: 

provisions 113 

phenomena 115 

of  the  Severn  and  Mersey  tunnels 58 

Variations  in  the  amount  of  dust  in  the  New  York  subway 188 

Valves  in  the  New  York  subway 120 

Vault  lights  in  the  New  York  subway 109 

Water  vapor  in  normal  atmosphere 18 

Waterloo  and  City  Railway •      3 

Weight  of  air 50 

of  dust  in  the  New  York  subway 178, 186,  200 

of  dust  inhaled  by  passengers  in  the  New  York  subway 187, 200 


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Manual  of  Assaying I2mo,  i  oo 

Minet's  Production  of  Aluminum  and  its  Industrial  Use.     (Waldo).. ....  i2mo,  2  50 

O'Driscoll's  Notes  on  the  Treatment  of  Gold  Ores 8vo,  2  oo 

Ricketts  and  Miller's  Notes  on  Assaying 8vo,  3  oo 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc) 8vo,  4  oo 

Ulke's  Modern  Electrolytic  Copper  Refining 8vo,  3  oo 

Wilson's  Chlorination  Process I2mo,  I  50 

Cyanide  Processes I2ma  r  50 


ASTRONOMY. 

Comstock's  Field  Astronomy  for  Engineers 8vo,  2  50 

Craig's  Azimuth 4to,  3  50 

Crandall's  Text-book  on  Geodesy  and  Least  Squares 8vo,  3  oo 

Doolittle's  Treatise  on  Practical  Astronomy. 8vo,  4  oo 

Gore's  Elements  of  Geodesy 8vo,  2  50 

Hayford's  Text-book  of  Geodetic  Astronomy 8vo,  3  oo 

Merriman's  Elements  of  Precise  Surveying  and  Geodesy 8vo,  2  50 

*  Michie  and  Harlow's  Practical  Astronomy 8vo,  3  oo 

Rust's  Ex -meridian  Altitude,  Azimuth  and  Star- Finding  Tables. 8vo,  5  oo 

*  White's  Elements  of  Theoretical  and  Descriptive  Astronomy X2mo,  2  oo 

3 


CHEMISTRY. 

*  Abderhalden's  Physiological  Chemistry  in  Thirty  Lectures.    (Hall  and  Defren) 

8vo,  5  oo 

*  Abegg's  Theory  of  Electrolytic  Dissociation,    (von  Ende) i2mo,  i  25 

Alexeyeff's  General  Principles  of  Organic  Syntheses.     (Matthews) 8vo,    3  oo 

Allen's  Tables  for  Iron  Analysis 8vo,  3  oo 

Arnold's  Compendium  of  Chemistry.     (Mandel) Large  i2mo,  3  50 

Association  of  State  and  National  Food  and  Dairy  Departments,  Hartford, 

Meeting,  1906 8vo,  3  oo 

Jamestown  Meeting,  1907 8vo,  3  oo 

Austen's  Notes  for  Chemical  Students : i2mo,  i  50 

Baskerville's  Chemical  Elements.     (In  Preparation.) 

Bernadou's  Smokeless  Powder. — Nitro-cellulose,  and  Theory  of  the  Cellulose 

Molecule ; i2mo;,  2  50 

Bilts's  Chemical  Preparations.     (Hall  and  Blanchard).     (In  Press.) 

*  Blanchard's  Synthetic  Inorganic  Chemistry. i2mo,  i  oo 

*  Browning's  Introduction  to  the  Rarer  Elements 8vo,  i  50 

Brush  and  Penfield's  Manual  of  Determinative  Mineralogy 8vo,  4  oo 

*  Claassen's  Beet-sugar  Manufacture.     (Hall  and  Rolfe) 8vo,  3  oo 

Classen's  Quantitative  Chemical  Analysis  by  Electrolysis.    (Boltwood)..  .8vo,  3  oo 

Cohn's  Indicators  and  Test-papers i2mo,  2  oo 

Tests  and  Reagents 8vo,  3  oo 

*  Danneel's  Electrochemistry.     (Merriam) i2mo,  i  25 

Dannerth's  Methods  of  Textile  Chemistry i2mo,  2  oo 

Duhem's  Thermodynamics  and  Chemistry.     (Burgess) 8vo,  4  oo 

Eakle's  Mineral  Tables  for  the  Determination  of  Minerals  by  their  Physical 

Properties 8vo,  i  25 

Eissler's  Modern  High  Explosives 8vo,  4  oo 

Eff rent's  Enzymes  and  their  Applications.     (Prescott) 8vo,  3  oo 

Erdmann's  Introduction  to  Chemical  Preparations.     (Dunlap) i2mo,  i  25 

*  Fischer's  Physiology  of  Alimentation Large  i2mo,  2  oo 

Fletcher's  Practical  Instructions  in  Quantitative  Assaying  with  the  Blowpipe. 

i2mo,  mor.  i  50 

Fowler's  Sewage  Works  Analyses i2mo,  2  oo 

Fresenius's  Manual  of  Qualitative  Chemical  Analysis.     (Wells) 8vo,  5  oo 

Manual  of  Qualitative  Chemical  Analysis.  Part  I.  Descriptive.  (Wells)  8vo,  3  oo 

Quantitative  Chemical  Analysis.     (Cohn)    2  vols -. 8vo,  12  50 

When  Sold  Separately,  Vol.  I,  $6.     Vol.  II,  $8. 

Fuertes's  Water  and  Public  Health izmo,  i  50 

Furman's  Manual  of  Practical  Assaying 8vo,  3  oo 

*  Getman's  Exercises  in  Physical  Chemistry i2mo,  2  oo 

Gill's  Gas  and  Fuel  Analysis  for  Engineers i2mo,  i  25 

*  Gooch  and  Browning's  Outlines  of  Qualitative  Chemical  Analysis. 

Large  i2mo,  i  25 

Grotenfelt's  Principles  of  Modern  Dairy  Practice.     (Wo II) i2mo,  2  oo 

Groth's  Introduction  to  Chenvcal  Crystallography  (Marshall) i2mo,  i  25 

Hammarsten's  Text-book  of  Physiological  Chemistry.     (Mandel) 8vo,  4  oo 

Hanausek's  Microscopy  of  Technical  Products.     (Winton) 8vo,  5  oo 

*  Haskins  and  Macleod's  Organic  Chemistry izmo,  2  oo 

Helm's  Principles  of  Mathematical  Chemistry.     (Morgan) i2mo,  i  50 

Bering's  Ready  Reference  Tables  (Conversion  Factors) i6mo,  mor.  2  50 

*  Herrick's  Denatured  or  Industrial  Alcohol 8vo,  4  oo 

Hinds's  Inorganic  Chemistry 8vo,  3  oo 

*  Laboratory  Manual  for  Students i2mo,  i  oo 

*  Holleman's    Laboratory   Manual    of   Organic    Chemistry  for   Beginners. 

(Walked ' i2mo,  i  oo 

Text-book  of  Inorganic  Chemistry.     (Cooper). . , 8vo,  2  50 

Text-book  of  Organic  Chemistry.     (Walker  and  Mott). . . . . , 8vo,  2  50 

4 


olley  and  Ladd's  Analysis  of  Mixed  Paints,  Color  Pigments,  and  Varnishes. 

Large  12 mo,  2  50 

Hopkins's  Oil-chemists'  Handbook 8vo,  3  oo 

Iddings's  Rock  Minerals 8vo,  5  oo 

Jackson's  Directions  for  Laboratory  Work  in  Physiological  Chemistry.  .8vo,  i  25 

Johannsen's  Determination  of  Rock-forming  Minerals  in  Thin  Sections  .  .8vo,  4  oo 
Johnson's  Chemical  Analysis  of  Special  Steel.     Steel-making.     (Alloys  and 
Graphite.)     (In  Press.) 

Keep's  Cast  Iron 8vo,  2  50 

Ladd's  Manual  of  Quantitative  Chemical  Analysis i2mo,  i  oo 

Landauer's  Spectrum  Analysis.     (Tingle) .  .   8vo,  3  oo 

*  Langwurtny  and   Austen's  Occurrence   of  Aluminium  in  Vegetable  Prod- 

ucts, Animal  Products,  and  Natural  Waters 8vo,  2  oo 

Lassar-Cohn's  Application  of  Some  General  Reactions  to  Investigations  in 

Organic  Chemistry.  (Tingle) I2mo,  i  oo 

Leach's  Inspection  and  Analysis  of  Food  with  Special  Reference  to  State 

Control 8vo,  7  50 

Lob's  Electrochemistry  of  Organic  Compounds.  (Lorenz) 8vo,  3  oo 

Lodge's  Notes  on  Assaying  and  Metallurgical  Laboratory  Experiments 8vo,  3  oo 

Low's  Technical  Method  of  Ore  Analysis 8vo,  3  oo 

Lunge's  Techno-chemical  Analysis.  (Conn)..' i2mo,  i  oo 

*  McKay  and  Larsen's  Principles  and  Practice  of  Butter-making 8vo,  I  50 

Maire's  Modern  Pigments  and  their  Vehicles i2mo,  2  oo 

Mandel's  Handbook  for  Bio-chemical  Laboratory i2mo,  i  50 

*  Martin's  Laboratory  Guide  to  Qualitative  Analysis  with  the  Blowpipe .  .  i2mo,  60 
Mason's  Examination  of  Water.     (Chemical  and  Bacteriological.).  .  .  .i2mo,  i  25 

.    Water-supply.     (Considered  Principally  from   a   Sanitary   Standpoint. 

8vo,  4  oo 

Mathewson's  Chemical  Theory  for  First  Year  College  Students.     (In  Press). 

Matthews's  Textile  Fibres.     2d  Edition,  Rewritten 8vo,  4  oo 


*  Meyer's  Determination  of  Radicle?  in  Carbon  Compounds.     (Tingle). .  i2mo, 
Miller's  Cyanide  Process i2mo, 

Manual  of  Assaying I2tno, 

Minet's  Production  of  Aluminum  and  its  Industrial  Use.  (Waldo) i2mo, 

Mixter's  Elementary  Text-book  of  Chemistry I2mo, 

Morgan's  Elements  of  Physical  Chemistry i  ?mo, 

Outline  of  the  Theory  of  Solutions  and  its  Results I2mo, 

*  Physical  Chemistry  for  Electrical  Engineers i2mo, 

Morse's  Calculations  used  in  Cane-sugar  Factories i6mo,  mor. 


25 
oo 
oo 
5P 
50 
oo 
oo 
50 
50 

*  Muir's  History  of  Chemical  Theories  and  Laws 8vo,     4  oo 

Mulliken's  General  Method  for  the  Identification  of  Pure  Organic  Compounds. 

Vol.  I Large  8vo,    5  oo 

O'Driscoll's  Notes  on  the  Treatment  of  Gold  Ores 8vo,    2  oo 

Ostwald's  Conversations  on  Chemistry.    Part  One.    (Ramsey) i2mo,     i  50 

"  "  "  Part  Two.     (Turabull) 12010,    2  oo 

*  Palmer's  Practical  Test  Book  of  Chemistry i2mo,     i  oo 

*  Pauli's  Physical  Chemistry  in  the  Service  of  Medicine.     (Fischer") I2mo,     i  25 

*  Penfield's  Notes  on  Determinative  Mineralogy  and  Record  of  Mineral  Tests. 

8vo,  paper,        50 
Tables  of  Minerals,  Including  the   Use   of  Minerals  and  Statistics  of 

Domestic  Production 8vo,    I  oo 

Pictet's  Alkaloids  and  their  Chemical  Constitution.     (Biddle) 8vo,    5  oo 

Podle's  Calorific  Power  of  Fuels 8vo,    3  oo 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Refer- 
ence to  Sanitary  Water  Analysis. . . I2mo,     i  50 

*  Reisig's  Guide  to  Piece-dyeing 8vo,  25  oo 

Richards  and  Woodman's  Air,  Water,  and  Food  from  a  Sanitary  Standpoint..8vo,    2  oo 

Ricketts  and  Miller's  Notes  on  Assaying 8vo,    3  oo 

Rideal's  Disinfection  and  the  Preservation  of  Food 8vo,    4  oo 

Sewage  and  the  Bacterial  Purification  of  Sewage 8vo,    4  oo 

5 


Riggs's  Elementary  Manual  for  the  Chemical  Laboratory 8vo,  i  25 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc) 8vo,  4  oo 

Ruddiman's  Incompatibilities  in  Prescriptions 8vo,  2  oo 

Whys  in  Pharmacy , .  i2mo,  i  oo 

Ruer's  Elements  of  Metallography.     (Mathewson)     (In  Preparation.) 

Sabin's  Industrial  and  Artistic  Technology  of  Paints  and  Varnish 8vo,  3  oo 

Salkowski's  Physiological  and  Pathological  Chemistry.     (Orndorff ) 8vo,  2  50 

Schimpf's  Essentials  of  Volumetric  Analysis I2mo,  i  25 

*  Qualitative  Chemical  Analysis 8vo,  i  25 

Text-book  of  Volumetric  Analysis I2mo,  2  50 

Smith's  Lecture  Notes  on  Chemistry  for  Dental  Students 8vo,  2  50 

Spencer's  Handbook  for  Cane  Sugar  Manufacturers i6mo,  mor.  3  oo 

Handbook  for  Chemists  of  Beet-sugar  Houses i6mo,  mor.  3  oo 

Stockbridge's  Rocks  and  Soils 8vo,  2  50 

*  Tillman's  Descriptive  General  Chemistry 8vo,  3  oo 

*  Elementary  Lessons  in  Heat 8vo,  i  50 

Treadwell's  Qualitative  Analysis.     (Hall) 8vo,  3  oo 

Quantitative  Analysis.     (Hall) 8vo,  4  oo 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Van  Deventer's  Physical  Chemistry  for  Beginners.     (Boltwood) i2mo,  i  50 

Venable's  Methods  and  Devices  for  Bacterial  Treatment  of  Sewage 8vo ,  3  oo 

Ward  and  Whipple's  Freshwater  Biology.     (In  Press.) 

Ware's  Beet-sugar  Manufacture  and  Refining.     Vol.  I Small  8vo,  4  oo 

V«1.  II SmallRvo,  500 

Washington's  Manual  of  the  Chemical  Analysis  of  Rocks 8vo,  2  oo 

*  Weaver's  Military  Explosives 8vo.  3  oo 

Wells's  Laboratory  Guide  in  Qualitative  Chemical  Analysis 8vo,  i  go 

Short  Course  in  Inorganic  Qualitative  Chemical  Analysis  for  Engineering 

Students , I2mo,  i  50 

Text-book  of  Chemical  Arithmetic I2mo,  i  25 

Whipple's  Microscopy  of  Drinking-water 8vo,'  3  50 

Wilson's  Chlorination  Process I2mo,  i  50 

Cyanide  Processes I2mo,  i  50 

Winton's  Microscopy  of  Vegetable  Foods 8vo,  7  50 

CIVIL  ENGINEERING. 

BRIDGES  AND  ROOFS.     HYDRAULICS.     MATERIALS  OF    ENGINEER- 
ING.    RAILWAY   ENGINEERING. 

Baker's  Engineers'  Surveying  Instruments 12 mo,  3  oo 

Bixby's  Graphical  Computing  Table Paper  19^  v  24!  inches.  25 

Breed  and  Hosmer's  Princioles  and  Practice  of  Surveying.     2  Volumes. 

Vol.  I.     Elementary  Surveying 8vo,  3  oo 

Vol.  II.     Higher  Surveying 8vo,  2  50 

*  Burr's  Ancient  and  Modern  Engineering  and  the  Isthmian  Canal 8vo,  3  50 

Comstock's  Field  Astronomy  for  Engineers 8vo,  2  50 

*  Corthell's  Allowable  Pressures  on  Deep  Foundations I2mo,  i  25 

Crandall's  Text-book  on  Geodesy  and  Least  Squares 8vo,  3  oo 

Davis's  Elevation  and  Stadia  Tables 8vo,  i  oo 

Elliott's  Engineering  for  Land  Drainage i2mo,  i  50 

Practical  Farm  Drainage i2mo,  T  t  oo 

*Fiebeger's  Treatise  on  Civil  Engineering 8vo,  5  oo 

Flemer's  Phototopographic  Methods  and  Instruments 8vo,  5"  oo 

Folwell's  Sewerage.     (Designing  and  Maintenance.) 8vo,  3  oo 

Freitag's  Architectural  Engineering 8vo,  3  50 

French  and  Ives's  Stereotomy 8vo,  2  50 

Goodhue's  Municipal  Improvements i2mo,  i  50 

Gore's  Elements  of  Geodesy 8vo,  2  50 

*  Hauch's  and  Rice's  Tables  of  Quantities  for  Preliminary  Estimates  . .  I2mo,  i  25 

6 


Hayford's  Text-book  of  Geodetic  Astronomy 8vo,  3  oo 

Bering's  Ready  Reference  Tables.     (Conversion  Factors) i6mo,  mor.  a  50 

Howe's  Retaining  Walls  for  Earth 1 2mo,  i  25 

*  Ives's  Adjustments  of  the  Engineer's  Transit  and  Level i6mo,  Bds.  25 

Ives  and  Hilts's  Problems  in  Surveying i6mo,  mor.  I  50 

Johnson's  (J.  B.)  Theory  and  Practice  of  Surveying Small  8vo,  4  oo 

Johnson's  (L.  J.)  Statics  by  Algebraic  and  Graphic  Methods 8vo,  2  oo 

Kinnicutt,  Winslow  and  Pratt's  Purification  of  Sewage.     (In  Preparation.) 
Laplace's    Philosophical   Essay    on    Probabilities.       (Truscott    and   Emory) 

121110,  2  oo 

Mahan's  Descriptive  Geometry 8vo,  i  50 

Treatise  on  Civil  Engineering.  ( 1873-)  (Wood) 8vo,  5  oo 

Merriman's  Elements  of  Precise  Surveying  and  Geodesy 8vo,  a  50 

Merriman  and  Brooks's  Handbook  for  Surveyors. i6mo,  mor.  2  oo 

Nugent's  Plane  Surveying 8vo,  3  50 

Ogden's  Sewer  Construction 8vo,  3  oo 

Sewer  Design i2mo,  2  oo 

Parsons's  Disposal  of  Municipal  Refuse.  . 8vo,  2  oo 

Patton's  Treatise  on  Civil  Engineering 8vo.  half  leather,  7  50 

Reed's  Topographical  Drawing  and  Sketching  4to,  5  oo 

Rideal's  Sewage  and  the  Bacterial  Purification  of  Sewage 8vo,  4  oo 

Riemer's  Shaft-sinking  under  Difficult  Conditions.  (Corning  and  Peele). .  8vo,  3  oo 

Siebert  and  Biggin's  Modern  Stone-cutting  and  Masonry 8vo,  i  50 

Smith's  Manual  of  Topographical  Drawing.  (McMillan) 8vo,  2  50 

Soper's  Air  and  Ventilation  of  Subways Large  i2mo,  2  50 

Tracy's  Plane  Surveying i6mo,  mor.  3  oo 

*  Trautwine's  Civil  Engineer's  Pocket-book i6mo,  mor.  5  oo 

Venable's  Garbage  Crematories  in  America 8vo,  2  oo 

Methods  and  Devices  for  Bacterial  Treatment  of  Sewage 8vo,  3  oo 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo,  6  oo 

Sheep,  6  50 

Law  of  Contracts 8vo,  3  oo 

Law  of  Operations  Preliminary  to  Construction  in  Engineering  and  Archi- 
tecture  8vo,  5  oo 

Sheep,  5  50 

Warren's  Stereotomy — Problems  in  Stone-cutting 8vo,  2  50 

*  Waterbury's  Vest-Pocket  Hand-book   of    Mat  icmatics   for   Engineers. 

a$X  si  inches,  mor.  i  oo 
Webb's  Problems  in  the  Use  and  Adjustment  of  Engineering  Instruments. 

i6mo,  mor.  i  25 

Wilson's  (H.  N.)  Topographic  Surveying .  8vo,  3  50 

Wilson's  (W.  L.)  Elements  of  Railroad  Track  and  Construction 12010,  2  oo 

BRIDGES  AND  ROOFS. 

Boiler's  Practical  Treatise  on  the  Construction  of  Iron  Highway  Bridges.  .8vo,  2  06 

Burr  and  Falk's  Design  and  Construction  of  Metallic  Bridges 8vc.  5  oo 

Influence  Lines  for  Bridge  and  Roof  Computations 8vo.  3  oo 

Du  Bo'.s's  Mechanics  of  Engineering.     Vol.  IL Err  all  4to,  10  oo 

Foster's  Treat'se  on  Wooden  Trestle  Bridges 4to,  5  oo 

Fowler's  Ordinary  Foundations 8vo,  3  50 

French  and  Ives's  Stereotomy 8vo,  2  50 

Greene's  Arches  in  Wood,  Iron,  and  Stone 8vo,  2  50 

Bridge  Trusses 8vo,  2  50 

Roof  Trusses 8vo,  i  25 

Grimm's  Secondary  Stresses  in  Bridge  Trusses 8vo,  2  50 

Heller's  Stresses  in  Structures  and  the  Accompanying  Deformations 8vo,  3  oo 

Howe's  Design  of  Simple  Roof -trusses  in  Wood  and  Steel 8vo,  a  oo 

Symmetrical  Masonry  Arches 8vo,  2  50 

Treatise  on  Arches 8vo,  4  oo 

7 


Johnson,  Bryan,  and  Turneaure's  Theory  and  Practice  in  the  Designing  of 

Modern  Framed  Structures Small  4to,  10  oo 

Merriman  and  Jacoby's  Text-book  on  Roofs  and  Bridges: 

Part  I.     Stresses  in  Simple  Trusses 8vo,  2  50 

Part  II.    Graphic  Statics 8vo,  2  50 

Part  III.  Bridge  Design 8vo,  2  50 

Part  IV.  Higher  Structures 8vo,  2  50 

Morison's  Memphis  Bridge Oblong  4to,  10  oo 

Sondericker's  Graphic  Statics,  with  Applications  to  Trusses,  Beams,  and  Arches. 

8vo,  2  oo 

Waddell's  De  Pontibus,  Pocket-book  for  Bridge  Engineers i6mo,  mor,  2  oo 

*  Specifications  for  Steel  Bridges i2mo,  50 

Waddelland  Harrington's  Bridge  Engineering.     (In  Preparation.) 

Wright's  Designing  of  Draw-spans.     Two  parts  in  one  volume 8vo,  3  50 

HYDRAULICS. 

Barnes's  Ice  Formation 8vo,  3  oo 

Bazin's  Experiments  upon  the  Contraction  of  the  Liquid  Vein  Issuing  from 

an  Orifice.     (Trautwine) 8vo,  2  oo 

Bovey's  Treatise  on  Hydraulics 8vo,  5  oo 

Church's  Diagrams  of  Mean  Velocity  of  Water  in  Open  Channels. 

Oblong  4to ,  paper,  i  50 

Hydraulic  Motors 8vo,  2  oo 

Mechanics  of  Engineering 8vo,  6  oo 

Coffin's  Graphical  Solution  of  Hydraulic  Problems i6mo,  mor.  2  50 

Flather's  Dynamometers,  and  the  Measurement  of  Power i2mo,  3  oo 

Folwell's  Water-supply  Engineering 8vo,  4  oo 

Frizell's  Water-power 8vo,  5  oo 

Fuertes's  Water  and  Public  Health « I2mo,  i  50 

Water-filtration  Works i2mo,  2  50 

Ganguillet  and  Kutter's  General  Formula  for  the  Uniform  Flow  of  Water  in 

Rivers  and  Other  Channels.     (Hering  and  Trautwine) 8vo,  4  oo 

Hazen's  Clean  Water  and  How  to  Get  It Large  i2mo,  i  50 

Filtration  of  Public  Water-supplies -. 8vo,  3  oo 

Hazlehurst's  Towers  and  Tanks  for  Water- works 8vo,  2  50 

Herschel's  115  Experiments  on  the  Carrying  Capacity  of  Large,  Riveted,  Metal 

Conduits '. 8vo,  2  oo 

Hoyt  and  Grover's  River  Discharge.. 8vo,  2  oo 

Hubbard  and  Kiersted's  Water-works  Management  and  Maintenance 8vo,  4  oo 

*  Lyndon's  Development  and  Electrical  Distribution  of  Water  Power.  . .  .8vo,  3  oo 
Mason's  Water-supply.     (Considered  Principally  from  a  Sanitary  Standpoint.) 

8vo,  4  oo 

Merriman's  Treatise  on  Hydraulics 8vo,  5  oo 

*  Michie's  Elements  of  Analytical  Mechanics 8vo,  4  oo 

*  Molitor's  Hydraulics  of  Rivers,  We.irs  and  Sluices 8vo,  2  oo 

Richards's  Laboratory  Notes  on  Industrial  Water  Analysis.     (In  Press), 
Schuyler's   Reservoirs  for  Irrigation,   Water-power,   and   Domestic   Water- 
supply Large  8vo,  5  oo 

*  Thoma-s  and  Watt's  Improvement  of  Rivers 4to,  6  oo 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Wegmann's  Design  and  Construction  of  Dams.     5th  Ed.,  enlarged 4to,  6  oo 

Water-supply  of  the  City  of  New  York  from  1658  to  1895 4to,  ICT  oo 

Whipple's  Value  of  Pure  Water Large  I2mo,  i  oo 

Williams  and  Hazen's  Hydraulic  Tables 8vo,  i  50 

Wilson's  Irrigation  Engineering Small  8vo,  4  oo 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  300 

Wood's  Elements  of  Analytical  Mechanics 8vo,  3  oo 

Turbines. 8vo,  2  50 

8 


MATERIALS  OF  ENGINEERING. 


Baker's  Roads  and  Pavements ; 8vo,  5  oo 

Treatise  on  Masonry  Construction 8vo,  5  oo 

Birkmire'u  Architectural  Iron  and  Steel 8vo,  3  50 

Compound  Riveted  Girders  as  Applied  in  Buildings 8vo,  2  oo 

Black's  United  States  Public  Works Oblong  4to.  5  oo 

Bleininger's  Manufacture  of  Hydraulic  Cement.     (In  Preparation.) 

*  Bovey's  Strength  of  Materials  and  Theory  of  Structures 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering 8vo,  7  50 

Byrne's  Highway  Construction 8vo,  5  oo 

Inspection  of  the  Materials  and  Workmanship  Employed  in  Construction. 

i6mo,  3  oo 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Du  Bois's  Mechanics  of  Engineering. 

Vol.   I.  Kinematics,  Statics,  Kinetics Small  4to,  7  SO 

Vol.  II.  'ihe  Stresses  in  Framed  Structures,  Strength  of  Materials  and 

Theory  of  Flexures Small  4to,  10  oo 

*Eckel's  Cements,  Limes,  and  Plasters 8vo,  6  oo 

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Constituents 8vo»  2  5<> 

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0 


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Molitor  and  Beard's  Manual  for  Resident  Engineers i6mo,  i  oo 

Nagle's  Field  Manual  for  Railroad  Engineers i6mo,  mor.  3  oo 

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Emch's  Introduction  to  Projective  Geojnetry  and  its  Applications 8vo,  2  50 

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MacCord's  Elements  of  Descriptive  Geometry. 8vo,  3  oc 

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10 


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Elements  of  Machine  Construction  and  Drawing 8vo,  7  50 

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11 


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Fiske's  Functions  of  a  Complex  Variable 8vo, 

Halsted's  Elementary  Synthetic  Geometry 8vo, 

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No.  2.  Synthetic  Projective  Geometry,  by  George  Bruce  Halsted. 
No.  3.  Determinants,  by  Laenas  Gifford  Weld.  No.  4.  Hyper- 
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Burr's  Elasticity  and  Resistance  of  the  Materials  of  Engineering 8vo,  7  50 

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Preservation  of  Timber 8vo,  a  oo 

Wood's  (M.  P.)  Rustless  Coatings:    Corrosion  and  Electrolysis  of  Iron  and 

Steel 8vo,  4  oo 

STEAM-ENGINES  AND  BOILERS. 

Berry's  Temperature-entropy  Diagram 1 2 mo,  i  25 

Carnot's  Reflections  on  the  Motive  Power  of  Heat.     (Thurston) i2mo,  I  50 

Chase's  Art  of  Pattern  Making 1 2010,  2  50 

Creighton's  Steim-engine  and  other  Heat-motors.  8vo,  500 

Dawson's  "  Engineering  "  and  Electric  Traction  Pocket-book iCmo,  mor.  5  oo 

Ford's  Boiler  Making  for  Boiler  Makers i8mo,  i  oo 

*  Gebhardt's  Steam  Power  Plant  Engineering 8vo,  6  oo 

Goss's  Locomotive  Performance 8vo,  5  oo 

Heraenway's  Indicator  Practice  and  Steam-engine  Economy I2mo,  2  oo 

Button's  Heat  and  Heat-engines 8vo,  5  oo 

Mechanical  Engineering  of  Power  Plants 8vo,  5  oo 

Kent's  Steam  boiler  Economy 8vo,  4  oo 

Kneass's  Practice  and  Theory  of  the  Injector 8vo,  i  50 

MacCord's  Slide-valves 8vo,  a  oo 

Meyer's  Modern  Locomotive  Construction 4to,  10  oo 

Moyer's  Steam  Turbines.     (Tn  Press.) 

Peabody's  Manual  of  the  Steam-engine  Indicator I2mo.  i  50 

Tables  of  the  Properties  of  Saturated  Steam  and  Other  Vapors 8vo,  i  oo 

Thermodynamics  of  the  Steam-engine  and  Other  Heat-engines 8vo,  5  oo 

Valve-gears  for  Steam-engines 8vo,  a  50 

Peabody  and  Miller's  Steam-borers 8vo,  4  oo 

Pray's  Twenty  Years  with  the  Indicator Large  8vo,  a  50 

Pupin's  Thermodynamics  of  Reversible  Cycles  in  Gases  and  Saturated  Vapors. 

(Osterbergl I2mo,  i  25 

Reagan's  Locomotives.    Simple,  Compound,  and  Electric.     New  Edition. 

Large  12 mo,  3  50 

Sinclair's  Locomotive  Engine  Running  and  Management I2mo,  a  oo 

Smart's  Handbook  of  Engineering  Laboratory  Practice xamo,  a  50 

Snow's  Steam-boiler  Practice 8vo,  3  oo 

Spangler's  Notes  on  Thermodynamics lamo,  i  oo 

Valve-gears , 8vo,  a  50 

Spangler.  Greene,  and  Marshall's  Elements  of  Steam-engineering 8vo,  3  oo 

Thomas's  Steam-turbines 8vo,  4  oo 

15 


Thurston's  Handbook  of  Engine  and  Boiler  Trials,  and  the  Use  of  the  Indi- 
cator and  the  Prony  Brake 8vo,  5  oo 

Handy  Tables 8vo,  i  50 

Manual  of  Steam-boilers,  their  resigns,  Construction,  and  Operation.. 8vo,  5  oo 

Thurston's  Manual  of  the  Steam-engine 2  vols.,  8vo,  10  oo 

Part  I.     History,  Structure,  and  Theory 8v:>,  6  oo 

Part  II.     Design,  Construction,  and  Operation 8vo,  6  oo 

Steam-boiler  Explosions  in  Theory  and  in  Practice i2mo,  i  50 

Wehrenfenning's  Analysis  and  Softening  of  Boiler  Feed-water  (Patterson)   8vo,  4  oo 

Weisbach's  Heat,  Steam,  and  Steam-engines.     (Du  Bois) 8vo,  5  oo 

Whitham's  Steam-engine  Design 8vo,  5  oo 

Wood's  Thermodynamicsi  Heat  Motors,  and  Refrigerating  Machines. .  .8vo,  4  oo 

MECHANICS  PURE  AND  APPLIED. 

Church's  Mechanics  of  Engineering 8vo,  6  oo 

Notes  and  Examples  in  Mechanics. . 8vo,  2  oo 

Dana's  Text-book  of  Elementary  Mechanics  for  Colleges  and  Schools.  .  i2mo,  i  50 
Du  Bois's  Elementary  Principles  of  Mechanics: 

Vol.      I.     Kinematics 8vo,  3  50 

VoL    II.     Statics 8vo,  4  oo 

Mechanics  of  Engineering.     Vol.    I Small  4to,  7  50 

VoL  II. Small  4to,  10  oo 

*  Greene's  Structural  Mechanics 8vo,  2  50 

James's  Kinematics  of  a  Point  and  the  Rational  Mechanics  of  a  Particle. 

Large  i2mo,  2  oo 

*  Johnson's  (W.  W.)  Theoretical  Mechanics I2mo.  3  oo 

Lanza's  Applied  Mechanics 8vo,  7  5<> 

*  Martin's  Text  Book  on  Mechanics,  Vol.  I,  Statics I2mo,  i  25 

*  Vol.  2,  Kinematics  and  Kinetics  .  .i2mo,  1  50 
Maurer's  Technical  Mechanics 8vo,  4  oo 

*  Merriman's  Elements  of  Mechanics I2mo,  I  oo 

Mechanics  of  Materials 8vo,  5  oo 

*  Michie's  Elements  of  Analytical  Mechanics 8vo,  4  oo 

Robinson's  Principles  of  Mechanism 8vo,  3  oo 

Sanborn's  Mechanics  Problems Large  i2mo,  i  50 

Schwamb  and  Merrill's  Elements  of  Mechanism 8vo,  3  oo 

Wood's  Elements  of  Analytical  Mechanics 3vo,  3  oo 

Principles  of  Elementary  Mechanics i2mo,  i  25 

MEDICAL. 

*  Abderhalden's  Physiological  Chemistry  in  Thirty  Lectures.    (Hall  and  Defren) 

8vo,  5  oo 

von  Behring's  Suppression  of  Tuberculosis.     (Bolduan) i2mo,  i  oo 

*  Bolduan's  Immune  Sera i2mo,  i  50 

Borders  Contribution  to  Immunity.     (Gay).     (In  Preparation.) 

Davenport's  Statistical  Methods  with  Special  Reference  to  Biological  Varia- 
tions  i6mo,  mor.  i  50 

Ehrlich's  Collected  Studies  on  Immunity.     (Bolduan) 8vo,  6  oo 

*  Fischer's  Physiology  of  Alimentation Large  12010,  cloth,  2  oo 

de  Fursac's  Manual  of  Psychiatry.     (Rosanoff  and  Collins) Large  i2mo,  2  50 

Hammarsten's  Text-book  on  Physiological  Chemistry.     (Mandel) .8vo,  4  oo 

Jackson's  Directions  for  Laboratory  Work  in  Physiological  Chemistry.  ..8vo,  25 

Lassar-Cohn's  Practical  Urinary  Analysis.     (Lorenz) I2mo,  •  oo 

Mandel's  Hand  Book  for  the  Bi  -  Chemical  Laboratory i2mo,  50 

*  Pauli's  Physical  Chemistry  in  the  Service  of  Medicine.     (Fischer) 12010,  25 

*  Pozzi-Escot's  Toxins  and  Venoms  and  their  Antibodies.     (Conn) i2mo,  oo 

Rostoski's  Serum  Diagnosis.     (Bolduan) '. .  I2mo,  oo 

Ruddiman's  Incompatibilities  in  Prescriptions , 8vo,  oo 

Whys  in  Pharmacy I2mo'  °° 

16 


Salkowski's  Physiological  and  Pathological  Chemistry.     (Orndorff) 8vo,  2  50 

*  Satterlee's  Outlines  of  Human  Embryology I2mo.  i   25 

Smith's  Lecture  Notes  on  Chemistry  for  Dental  Students 8vo,  2  50 

Steel's  Treatise  on  the  Diseases  of  the  Dog .  8vo,  3  50 

*  Whipple's  Typhoid  Fever : Large  i2mo,  3  oo 

Woodhull's  Notes  on  Military  Hygiene i6mo,  i  50 

*  Personal  Hvp-'ene I2mo,  z  oo 

Worcester  and  Atkinson's  Small  Hospitals  Establishment  and  Maintenance, 

and  S  ggestions  for  Hospital  Architecture,  with  Plans  for  a  Small 

Hospital 1 2ino,  i  23 

METALLURGY. 

Betts's  Lead  Refining  by  Electrolysis 8vo,  4  oo 

Holland's  Encyclopedia  of  Founding  and  Dictionary  of  Foundry  Terms  Used 

in  the  Practice  of  Moulding i2mo,  3  oo 

Iron  Founder 1 2mo,  2  50 

"           "        Supplement i2mo,  2  50 

Douglas's  Untechnical  Addresses  on  Technical  Subjects i2mo,  i  oo 

Goesel's  Minerals  and  Metals:  A  Reference  Book i6mo,  mor.  3  oc 

*  Iles's  Lead-smelting i2mo,  2  50 

Keep's  Cast  Iron 8vo,  2  50 

LeChatelier's  High-temperature  Measurements.   (Boudouard — Burgess)  i2mo,  3  oo 

Metcalf's  Steel.     A  Manual  for  Steel-users i2mo,  2  oo 

Miller's  Cyanide  Process i2mo,  i  oo 

Minet's  Production  of  Aluminium  and  its  Industrial  Use.    (Waldo)  .  .  .i2mo,  2  50 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc) 8vo,  4  oo 

Ruer's  Elements  of  Metallography.     (Mathewson)     (In  Press.) 

Smith's  Materials  of  Machines i2mo,  i  oo 

Tate  and  Stone's  Foundry  Practice.     (In  Press.) 

Thurston's  Materials  of  Engineering.     In  Three  Parts 8vo,  8  oo 

Parti.         Non-metallic  Materials  of  Engineering  and  Metallurgy.  .  .8vo,  200 

Part  II.       Iron  and  Steel 8vo,  3  50 

Part  III.     A  Treatise  on  Brasses,  Bronzes,  and  Other  Alloys  and  their 

Constituents 8vo,  2  50 

Hike's  Modern  Electrolytic  Copper  Refining 8vo,  3  oo 

West's  American  Foundry  Practice I2mo,  2  50 

Moulder's  Text  Book    I2mo,  2  50 

Wilson's  Chlorination  Process 12 mo,  i   50 

Cyanide  Processes i2mo,  i  50 

MINERALOGY. 

Barringer's  Description  of  Minerals  of  Commercial  Value Oblong,  mor.  2  50 

Boyd's  Resources  of  Southwest  Virginia 8vo,  3  oo 

Boyd's  Map  of  Southwest  Virginia. Pocket-book  form.  2  oo 

*  Browning's  Introduction  to  the  Rarer  Elements 8vo,  i  50 

Brush's  Manual  of  Determinative  Mineralogy.     (Penfield) 8vo,  4  oo 

Butler's  Pocket  Hand-Book  of  Minerals i6mo,  mor.  3  oo 

Chester's  Catalogue  of  Minerals 8vo,  paper,  i  oo 

Cloth,  i  25 

*Crane's  Gold  and  Silver. 8vo,  5  oo 

Dana's  First  Appendix  to  Dana's  New  "  System  of  Mineralogy..".  .Large  8vo,  i  oo 

Manual  of  Mineralogy  and  Petrography I2mo  2  oo 

Minerals  and  How  to  Study  Them I2mo,  r  50 

System  of  Mineralogy Large  8vo,  half  leather,  12  50 

Text-book  of  Mineralogy 8vo,  4  oo 

Douglas's  Untechnical  Addresses  on  Technical  Subjects I2mo,  i  oo 

Eakle's  Mineral  Tables 8vo,  i  25 

Stone  and  Clay  Products  Used  in  Engineering .     ( In  Preparation . ) 
17 


Egleston's  Catalogue  of  Minerals  and  Synonyms 8vo,  2  50 

Goesel's  Minerals  and  Metals :     A  Reference  Book i6mo  mor.  3  oo 

Groth's  Introduction  to  Chemical  Crystallography  (Marshall) 12 mo,  i  23 

*  Iddmps's  Rock  Minerals   .    8vo,  5  oo 

Johannsen's  Determination  of  Rock-forming  Minerals  in  Thin  Sections 8vo,  4  oo 

*  Martin's  Laboratory  Guide  to  Qualitative  Analysis  with  the  Blowpipe.  I2mo,  60 
Merrill's  Non-metallic  Minerals:  Their  Occurrence  and  Uses 8vo,  4  oo 

Stones  for  Building  and  Decoration 8vo,  500 

*  Penfield's  Notes  on  Determinative  Mineralogy  and  Record  of  Mineral  Tests. 

8vo,  paper,  50 
Tables    of    Minerals,    Including    the  Use  of  Minerals  and  Statistics  of 

Domestic  Production 8vo,  i  oo 

*  Pirsson's  Rocks  and  Rock  Minerals I2mo,  2  50 

*  Richards's  Synopsis  ot  Mineral  Characters I2mo,  mor,  i  25 

*  Ries's  Clays:  Their  Occurrence   Properties,  and  Uses.. 8vo,  5  oo 

*  Tillman's  Text-book  of  Important  Minerals  and  Rocks 8vo,  2  oo 

MINING. 

*  Beard's  Mine  Gases  and  Explosions Large  i2mo,  3  oo 

Boyd's  Map  of  Southwest  Vhginia Pocket-oook  rorm,  2  oo 

Resources  of  Southwest  Virginia 8vo,  3  oo 

*  Crane's  Gold  and  Silver    8vo,  5  oo 

Douglas's  Untechnical  Addresses  on  Technical  Subjects I2mo-,  I  oo 

Eissler's  Modern  High  Explosives Svo,  4  oo 

Goesel's  Minerals  and  Metals :    A  Reference  Book i6mo,  mor.  3  oo 

I  Iseng's  Manual  of  Mining 8vo,  5  oo 

*  Iles's  Lead-smelting I2mo,  2  50 

Miller's  Cyanide  Process I2mo,  i  oo 

O'Driscoll's  Notes  on  the  Treatment  of  Gold  Ores Svo,  2  oo 

Peele's  Compressed  Ah"  Plant  for  Mines Svo,  3  oo 

Riemer's  Shaft  Sinking  Under  Difficult  Conditions.     (Corning  and  Peele) . .  .8vo,  3  oo 

Robine  and  Lenglen's  Cyanide  Industry.     (Le  Clerc) Svo,  4  oo 

*  Weaver's  Military  Explosives Svo,  3  oo 

Wilson's  Chlorination  Process limo,  i  50 

Cyanide  Processes I2mo,  I  50 

Hydraulic  and  Placer  Mining.     2d  edition,  rewritten I2mo,  2  50 

Treatise  on  Practical  and  Theoretical  Mine  Ventilation I2mo,  i  25 

SANITARY  SCIENCE. 

Association  of  State  and  National  Food  and  Dairy  Departments,  Hartford  Meeting, 

1906 Svo,  3  oo 

Jamestown  Meeting,  1907 8vo,  3  oo 

*  Bashore's  Outlines  of  Practical  Sanitation i2mo,  i  25 

Sanitation  ot  a  Country  House I2mo,  i  oo 

Sanitation  of  Recreation  Camps  and  Parks I2mo,  i  oo 

Folwell's  Sewerage.     (Designing,  Construction,  and  Maintenance) Svo,  3  oo 

Water-supply  Engineering Svo,  4  oo 

Fowler's  Sewage  Works  Analyses I2mo,  2  oo 

Fuertes's  Water-filtration  Works I2mo, 

Water  and  Public  Health I2mo, 

Gerhard's  Guide  to  Sanitary  House-inspection i6mo, 

*  Modern  Baths  and  Bath  Houses Svo, 

Sanitation  of  Public  Buildings ,• I2mo, 

Hazen's  Clean  Water  and  How  to  Get  It I*rge  i2mo, 

Filtration  of  Public  Water-supplies. Svo.  3  oo 

Kinnicut,  Winslow  and  Pratt's  Purification  of  Sewage.     (In  Press.) 

Leach's   Inspection   and   Analysis  of  Food  with  Special  Reference  to  State 

Control Svo.  7  oo 

18 


50 
So 

00 

00 

50 

50 


Mason's  Examination  of  Water.     (Chemical  and  Bacteriological) i2mo,  i  35 

Water-supply.  (Considered  Principally  from  a  Sanitary  Standpoint) . .  8vo,  4  oo 

*  Merriman's  Elements  of  Sanitary  Engineering 8vo,  2  oo 

Ogden's  Sewer  Design. izmo,  2  oo 

Parsons's  Disposal  of  Municipal  Refuse 8vo,  2  oo 

Prescott  and  Winslow's  Elements  of  Water  Bacteriology,  with  Special  Refer- 
ence to  Sanitary  Water  Analysis lamo,  i  50 

*  Price's  Handbook  on  Sanitation i2mo,  i  50 

Richards's  Cost  of  Cleanness.     A  Twentieth  Century  Problem i2mo,  i  oo 

Cost  of  Food.     A  Study  in  Dietaries i2mo,  i  oo 

Cost  of  Living  as  Modified  by  Sanitary  Science I2mo,  i  oo 

Cost  of  Shelter.    A  Study  in  Economics izrno,  i  oo 

*  Richards  and  Williams's  Dietary  Computer 8vo,  i  50 

Richards  and   Woodman's  Air,   Water,  and  Food  from  a  Sanitary  Stand- 
point  8vo,  2  oo 

Rideal's   Disinfection  and  the  Preservation  of  Food 8vo,  4  oo 

Sewage  and  Bacterial  Purification  of  Sewage 8vo,  4  oo 

Sopor's  Air  and  Ventilation  of  Subways Large  i2mo,  2  50 

Turneaure  and  Russell's  Public  Water-supplies 8vo,  5  oo 

Venable's  Garbage  Crematories  in  America 8vo,  2  oo 

Method  and  Devices  for  Bacterial  Treatment  of  Sewage 8vo,  3  oo 

Ward  and  Whipple's  Freshwater  Biology i2iuo,  2  50 

Whipple's  Microscopy  of  Drinking-water 8vo,  3  50 

Typhod  Fever Large  i2mo,  3  oo 

Value  of  Pure  Water Large  i2mo,  i  oo 

Winslow's  Bacterial  Classification i2mo,  2  50 

Winton's  Microscopy  of  Vegetable  Foods 8vo,  7  50 

MISCELLANEOUS. 

Emmons's  Geological  Guide-book  of  the  Rocky  Mountain  Excursion  of  the 

International  Congress  of  Geologists Large  8vo,  i  50 

Ferret's  Popular  Treatise  on  the  Winds 8vo,  4  oo 

Fitzgerald's  Boston  Machinist i8mo,  i  oo 

Gannett's  Statistical  Abstract  of  the  World 24010,  75 

Haines's  American  Railway  Management i2mo,  2  50 

*  Hanusek's  The  Microscopy  of  Technical  Products.    (Winton) 8vo,  5  oo 

Owen's  The  Dyeing  and  Cleaning  of  Textile  Fabrics.     (Standage ).     (In  Press.) 
Ricketts's  History  of  Rensselaer  Polytechnic  Institute   1824-1894. 

Large  12  mo,  3  oo 

Rotherham's  Emphasized  New  Testament Large  8vo,  2  oo 

Standage's  Decoration  of  Wood,  Glass,  Metal,  etc i2mo,  2  oo 

Thome's  Structural  and  Physiological  Botany.    (Bennett) i6mo,  2  25 

Westermaier's  Compendium  of  General  Botany.     (Schneider) 8vo,  2  oo 

Winslow's  Elements  of  Applied  Microscopy I2mo,  x  50 


HEBREW  AND  CHALDEE  TEXT-BOOKS. 

Green's  Elementary  Hebrew  Grammar 1 2010,     i  25 

Geaenius's  Hebrew  and  Chaldee  Lexicon  to  the  Old  Testament  Scriptures. 

(Tregelles) Small  4to,  half  mor.    5  oo 

19 


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